This repo contains solutions for projecteuler problems. Specially created for newcomers to contribute as part of Hacktoberfest Challenge.
Kind request to everyone that before sending any pull request test your solutions on projecteuler.net.
- Problem #1 Multiples of 3 and 5 || solutions
- Problem #2 Even Fibonacci numbers || solutions
- Problem #3 Largest prime factor || solutions
- Problem #4 Largest palindrome product || solutions
- Problem #5 Smallest multiple || solutions
- Problem #6 Sum square difference || solutions
- Problem #7 10001st prime || solutions
- Problem #8 Largest product in a series || solutions
- Problem #9 Special Pythagorean triplet || solutions
- Problem #10 Summation of primes || solutions
- Problem #11 Largest product in a grid || solutions
- Problem #12 Highly divisible triangular number || solutions
- Problem #13 Large sum || solutions
- Problem #14 Longest Collatz sequence || solutions
- Problem #15 Lattice paths || solutions
- Problem #16 Power digit sum || solutions
- Problem #17 Number letter counts || solutions
- Problem #18 Maximum path sum I || solutions
- Problem #19 Counting Sundays || solutions
- Problem #20 Factorial digit sum || solutions
- Problem #21 Amicable numbers || solutions
- Problem #22 Names scores || solutions
- Problem #23 Non-abundant sums || solutions
- Problem #24 Lexicographic permutations || solutions
- Problem #25 1000-digit Fibonacci number || solutions
- Problem #26 Reciprocal cycles || solutions
- Problem #27 Quadratic primes || solutions
- Problem #28 Number spiral diagonals || solutions
- Problem #29 Distinct powers || solutions
- Problem #30 Digit fifth powers || solutions
- Problem #31 Coin sums || solutions
- Problem #32 Pandigital products || solutions
- Problem #33 Digit cancelling fractions || solutions
- Problem #34 Digit factorials || solutions
- Problem #35 Circular primes || solutions
- Problem #36 Double-base palindromes || solutions
- Problem #37 Truncatable primes || solutions
- Problem #38 Pandigital multiples || solutions
- Problem #39 Integer right triangles || solutions
- Problem #40 Champernowne's constant || solutions
- Problem #41 Pandigital prime || solutions
- Problem #42 Coded triangle numbers || solutions
- Problem #43 Sub-string divisibility || solutions
- Problem #44 Pentagon numbers || solutions
- Problem #45 Triangular, pentagonal, and hexagonal || solutions
- Problem #46 Goldbach's other conjecture || solutions
- Problem #47 Distinct primes factors || solutions
- Problem #48 Self powers || solutions
- Problem #49 Prime permutations || solutions
- Problem #50 Consecutive prime sum || solutions
- Problem #51 Prime digit replacements || solutions
- Problem #52 Permuted multiples || solutions
- Problem #53 Combinatoric selections || solutions
- Problem #54 Poker hands || solutions
- Problem #55 Lychrel numbers || solutions
- Problem #56 Powerful digit sum || solutions
- Problem #57 Square root convergents || solutions
- Problem #58 Spiral primes || solutions
- Problem #59 XOR decryption || solutions
- Problem #60 Prime pair sets || solutions
- Problem #61 Cyclical figurate numbers || solutions
- Problem #62 Cubic permutations || solutions
- Problem #63 Powerful digit counts || solutions
- Problem #64 Odd period square roots || solutions
- Problem #65 Convergents of e || solutions
- Problem #66 Diophantine equation || solutions
- Problem #67 Maximum path sum II || solutions
- Problem #68 Magic 5-gon ring || solutions
- Problem #69 Totient maximum || solutions
- Problem #70 Totient permutation || solutions
- Problem #71 Ordered fractions || solutions
- Problem #72 Counting fractions || solutions
- Problem #73 Counting fractions in a range || solutions
- Problem #74 Digit factorial chains || solutions
- Problem #75 Singular integer right triangles || solutions
- Problem #76 Counting summations || solutions
- Problem #77 Prime summations || solutions
- Problem #78 Coin partitions || solutions
- Problem #79 Passcode derivation || solutions
- Problem #80 Square root digital expansion || solutions
- Problem #81 Path sum: two ways || solutions
- Problem #82 Path sum: three ways || solutions
- Problem #83 Path sum: four ways || solutions
- Problem #84 Monopoly odds || solutions
- Problem #85 Counting rectangles || solutions
- Problem #86 Cuboid route || solutions
- Problem #87 Prime power triples || solutions
- Problem #88 Product-sum numbers || solutions
- Problem #89 Roman numerals || solutions
- Problem #90 Cube digit pairs || solutions
- Problem #91 Right triangles with integer coordinates || solutions
- Problem #92 Square digit chains || solutions
- Problem #93 Arithmetic expressions || solutions
- Problem #94 Almost equilateral triangles || solutions
- Problem #95 Amicable chains || solutions
- Problem #96 Su Doku || solutions
- Problem #97 Large non-Mersenne prime || solutions
- Problem #98 Anagramic squares || solutions
- Problem #99 Largest exponential || solutions
- Problem #100 Arranged probability || solutions
- Problem #101 Optimum polynomial || solutions
- Problem #102 Triangle containment || solutions
- Problem #103 Special subset sums: optimum || solutions
- Problem #104 Pandigital Fibonacci ends || solutions
- Problem #105 Special subset sums: testing || solutions
- Problem #106 Special subset sums: meta-testing || solutions
- Problem #107 Minimal network || solutions
- Problem #108 Diophantine reciprocals I || solutions
- Problem #109 Darts || solutions
- Problem #110 Diophantine reciprocals II || solutions
- Problem #111 Primes with runs || solutions
- Problem #112 Bouncy numbers || solutions
- Problem #113 Non-bouncy numbers || solutions
- Problem #114 Counting block combinations I || solutions
- Problem #115 Counting block combinations II || solutions
- Problem #116 Red, green or blue tiles || solutions
- Problem #117 Red, green, and blue tiles || solutions
- Problem #118 Pandigital prime sets || solutions
- Problem #119 Digit power sum || solutions
- Problem #120 Square remainders || solutions
- Problem #121 Disc game prize fund || solutions
- Problem #122 Efficient exponentiation || solutions
- Problem #123 Prime square remainders || solutions
- Problem #124 Ordered radicals || solutions
- Problem #125 Palindromic sums || solutions
- Problem #126 Cuboid layers || solutions
- Problem #127 abc-hits || solutions
- Problem #128 Hexagonal tile differences || solutions
- Problem #129 Repunit divisibility || solutions
- Problem #130 Composites with prime repunit property || solutions
- Problem #131 Prime cube partnership || solutions
- Problem #132 Large repunit factors || solutions
- Problem #133 Repunit nonfactors || solutions
- Problem #134 Prime pair connection || solutions
- Problem #135 Same differences || solutions
- Problem #136 Singleton difference || solutions
- Problem #137 Fibonacci golden nuggets || solutions
- Problem #138 Special isosceles triangles || solutions
- Problem #139 Pythagorean tiles || solutions
- Problem #140 Modified Fibonacci golden nuggets || solutions
- Problem #141 Investigating progressive numbers, n, which are also square || solutions
- Problem #142 Perfect Square Collection || solutions
- Problem #143 Investigating the Torricelli point of a triangle || solutions
- Problem #144 Investigating multiple reflections of a laser beam || solutions
- Problem #145 How many reversible numbers are there below one-billion? || solutions
- Problem #146 Investigating a Prime Pattern || solutions
- Problem #147 Rectangles in cross-hatched grids || solutions
- Problem #148 Exploring Pascal's triangle || solutions
- Problem #149 Searching for a maximum-sum subsequence || solutions
- Problem #150 Searching a triangular array for a sub-triangle having minimum-sum || solutions
- Problem #151 Paper sheets of standard sizes: an expected-value problem || solutions
- Problem #152 Writing 1/2 as a sum of inverse squares || solutions
- Problem #153 Investigating Gaussian Integers || solutions
- Problem #154 Exploring Pascal's pyramid || solutions
- Problem #155 Counting Capacitor Circuits || solutions
- Problem #156 Counting Digits || solutions
- Problem #157 Solving the diophantine equation 1/a+1/b= p/10n || solutions
- Problem #158 Exploring strings for which only one character comes lexicographically after its neighbour to the left || solutions
- Problem #159 Digital root sums of factorisations || solutions
- Problem #160 Factorial trailing digits || solutions
- Problem #161 Triominoes || solutions
- Problem #162 Hexadecimal numbers || solutions
- Problem #163 Cross-hatched triangles || solutions
- Problem #164 Numbers for which no three consecutive digits have a sum greater than a given value || solutions
- Problem #165 Intersections || solutions
- Problem #166 Criss Cross || solutions
- Problem #167 Investigating Ulam sequences || solutions
- Problem #168 Number Rotations || solutions
- Problem #169 Exploring the number of different ways a number can be expressed as a sum of powers of 2 || solutions
- Problem #170 Find the largest 0 to 9 pandigital that can be formed by concatenating products || solutions
- Problem #171 Finding numbers for which the sum of the squares of the digits is a square || solutions
- Problem #172 Investigating numbers with few repeated digits || solutions
- Problem #173 Using up to one million tiles how many different "hollow" square laminae can be formed? || solutions
- Problem #174 Counting the number of "hollow" square laminae that can form one, two, three, ... distinct arrangements || solutions
- Problem #175 Fractions involving the number of different ways a number can be expressed as a sum of powers of 2 || solutions
- Problem #176 Right-angled triangles that share a cathetus || solutions
- Problem #177 Integer angled Quadrilaterals || solutions
- Problem #178 Step Numbers || solutions
- Problem #179 Consecutive positive divisors || solutions
- Problem #180 Rational zeros of a function of three variables || solutions
- Problem #181 Investigating in how many ways objects of two different colours can be grouped || solutions
- Problem #182 RSA encryption || solutions
- Problem #183 Maximum product of parts || solutions
- Problem #184 Triangles containing the origin || solutions
- Problem #185 Number Mind || solutions
- Problem #186 Connectedness of a network || solutions
- Problem #187 Semiprimes || solutions
- Problem #188 The hyperexponentiation of a number || solutions
- Problem #189 Tri-colouring a triangular grid || solutions
- Problem #190 Maximising a weighted product || solutions
- Problem #191 Prize Strings || solutions
- Problem #192 Best Approximations || solutions
- Problem #193 Squarefree Numbers || solutions
- Problem #194 Coloured Configurations || solutions
- Problem #195 Inscribed circles of triangles with one angle of 60 degrees || solutions
- Problem #196 Prime triplets || solutions
- Problem #197 Investigating the behaviour of a recursively defined sequence || solutions
- Problem #198 Ambiguous Numbers || solutions
- Problem #199 Iterative Circle Packing || solutions
- Problem #200 Find the 200th prime-proof sqube containing the contiguous sub-string "200" || solutions
- Problem #201 Subsets with a unique sum || solutions
- Problem #202 Laserbeam || solutions
- Problem #203 Squarefree Binomial Coefficients || solutions
- Problem #204 Generalised Hamming Numbers || solutions
- Problem #205 Dice Game || solutions
- Problem #206 Concealed Square || solutions
- Problem #207 Integer partition equations || solutions
- Problem #208 Robot Walks || solutions
- Problem #209 Circular Logic || solutions
- Problem #210 Obtuse Angled Triangles || solutions
- Problem #211 Divisor Square Sum || solutions
- Problem #212 Combined Volume of Cuboids || solutions
- Problem #213 Flea Circus || solutions
- Problem #214 Totient Chains || solutions
- Problem #215 Crack-free Walls || solutions
- Problem #216 Investigating the primality of numbers of the form 2n2-1 || solutions
- Problem #217 Balanced Numbers || solutions
- Problem #218 Perfect right-angled triangles || solutions
- Problem #219 Skew-cost coding || solutions
- Problem #220 Heighway Dragon || solutions
- Problem #221 Alexandrian Integers || solutions
- Problem #222 Sphere Packing || solutions
- Problem #223 Almost right-angled triangles I || solutions
- Problem #224 Almost right-angled triangles II || solutions
- Problem #225 Tribonacci non-divisors || solutions
- Problem #226 A Scoop of Blancmange || solutions
- Problem #227 The Chase || solutions
- Problem #228 Minkowski Sums || solutions
- Problem #229 Four Representations using Squares || solutions
- Problem #230 Fibonacci Words || solutions
- Problem #231 The prime factorisation of binomial coefficients || solutions
- Problem #232 The Race || solutions
- Problem #233 Lattice points on a circle || solutions
- Problem #234 Semidivisible numbers || solutions
- Problem #235 An Arithmetic Geometric sequence || solutions
- Problem #236 Luxury Hampers || solutions
- Problem #237 Tours on a 4 x n playing board || solutions
- Problem #238 Infinite string tour || solutions
- Problem #239 Twenty-two Foolish Primes || solutions
- Problem #240 Top Dice || solutions
- Problem #241 Perfection Quotients || solutions
- Problem #242 Odd Triplets || solutions
- Problem #243 Resilience || solutions
- Problem #244 Sliders || solutions
- Problem #245 Coresilience || solutions
- Problem #246 Tangents to an ellipse || solutions
- Problem #247 Squares under a hyperbola || solutions
- Problem #248 Numbers for which Euler’s totient function equals 13! || solutions
- Problem #249 Prime Subset Sums || solutions
- Problem #250 250250 || solutions
- Problem #251 Cardano Triplets || solutions
- Problem #252 Convex Holes || solutions
- Problem #253 Tidying up || solutions
- Problem #254 Sums of Digit Factorials || solutions
- Problem #255 Rounded Square Roots || solutions
- Problem #256 Tatami-Free Rooms || solutions
- Problem #257 Angular Bisectors || solutions
- Problem #258 A lagged Fibonacci sequence || solutions
- Problem #259 Reachable Numbers || solutions
- Problem #260 Stone Game || solutions
- Problem #261 Pivotal Square Sums || solutions
- Problem #262 Mountain Range || solutions
- Problem #263 An engineers' dream come true || solutions
- Problem #264 Triangle Centres || solutions
- Problem #265 Binary Circles || solutions
- Problem #266 Pseudo Square Root || solutions
- Problem #267 Billionaire || solutions
- Problem #268 Counting numbers with at least four distinct prime factors less than 100 || solutions
- Problem #269 Polynomials with at least one integer root || solutions
- Problem #270 Cutting Squares || solutions
- Problem #271 Modular Cubes, part 1 || solutions
- Problem #272 Modular Cubes, part 2 || solutions
- Problem #273 Sum of Squares || solutions
- Problem #274 Divisibility Multipliers || solutions
- Problem #275 Balanced Sculptures || solutions
- Problem #276 Primitive Triangles || solutions
- Problem #277 A Modified Collatz sequence || solutions
- Problem #278 Linear Combinations of Semiprimes || solutions
- Problem #279 Triangles with integral sides and an integral angle || solutions
- Problem #280 Ant and seeds || solutions
- Problem #281 Pizza Toppings || solutions
- Problem #282 The Ackermann function || solutions
- Problem #283 Integer sided triangles for which the area/perimeter ratio is integral || solutions
- Problem #284 Steady Squares || solutions
- Problem #285 Pythagorean odds || solutions
- Problem #286 Scoring probabilities || solutions
- Problem #287 Quadtree encoding (a simple compression algorithm) || solutions
- Problem #288 An enormous factorial || solutions
- Problem #289 Eulerian Cycles || solutions
- Problem #290 Digital Signature || solutions
- Problem #291 Panaitopol Primes || solutions
- Problem #292 Pythagorean Polygons || solutions
- Problem #293 Pseudo-Fortunate Numbers || solutions
- Problem #294 Sum of digits - experience #23 || solutions
- Problem #295 Lenticular holes || solutions
- Problem #296 Angular Bisector and Tangent || solutions
- Problem #297 Zeckendorf Representation || solutions
- Problem #298 Selective Amnesia || solutions
- Problem #299 Three similar triangles || solutions
- Problem #300 Protein folding || solutions
- Problem #301 Nim || solutions
- Problem #302 Strong Achilles Numbers || solutions
- Problem #303 Multiples with small digits || solutions
- Problem #304 Primonacci || solutions
- Problem #305 Reflexive Position || solutions
- Problem #306 Paper-strip Game || solutions
- Problem #307 Chip Defects || solutions
- Problem #308 An amazing Prime-generating Automaton || solutions
- Problem #309 Integer Ladders || solutions
- Problem #310 Nim Square || solutions
- Problem #311 Biclinic Integral Quadrilaterals || solutions
- Problem #312 Cyclic paths on Sierpiński graphs || solutions
- Problem #313 Sliding game || solutions
- Problem #314 The Mouse on the Moon || solutions
- Problem #315 Digital root clocks || solutions
- Problem #316 Numbers in decimal expansions || solutions
- Problem #317 Firecracker || solutions
- Problem #318 2011 nines || solutions
- Problem #319 Bounded Sequences || solutions
- Problem #320 Factorials divisible by a huge integer || solutions
- Problem #321 Swapping Counters || solutions
- Problem #322 Binomial coefficients divisible by 10 || solutions
- Problem #323 Bitwise-OR operations on random integers || solutions
- Problem #324 Building a tower || solutions
- Problem #325 Stone Game II || solutions
- Problem #326 Modulo Summations || solutions
- Problem #327 Rooms of Doom || solutions
- Problem #328 Lowest-cost Search || solutions
- Problem #329 Prime Frog || solutions
- Problem #330 Euler's Number || solutions
- Problem #331 Cross flips || solutions
- Problem #332 Spherical triangles || solutions
- Problem #333 Special partitions || solutions
- Problem #334 Spilling the beans || solutions
- Problem #335 Gathering the beans || solutions
- Problem #336 Maximix Arrangements || solutions
- Problem #337 Totient Stairstep Sequences || solutions
- Problem #338 Cutting Rectangular Grid Paper || solutions
- Problem #339 Peredur fab Efrawg || solutions
- Problem #340 Crazy Function || solutions
- Problem #341 Golomb's self-describing sequence || solutions
- Problem #342 The totient of a square is a cube || solutions
- Problem #343 Fractional Sequences || solutions
- Problem #344 Silver dollar game || solutions
- Problem #345 Matrix Sum || solutions
- Problem #346 Strong Repunits || solutions
- Problem #347 Largest integer divisible by two primes || solutions
- Problem #348 Sum of a square and a cube || solutions
- Problem #349 Langton's ant || solutions
- Problem #350 Constraining the least greatest and the greatest least || solutions
- Problem #351 Hexagonal orchards || solutions
- Problem #352 Blood tests || solutions
- Problem #353 Risky moon || solutions
- Problem #354 Distances in a bee's honeycomb || solutions
- Problem #355 Maximal coprime subset || solutions
- Problem #356 Largest roots of cubic polynomials || solutions
- Problem #357 Prime generating integers || solutions
- Problem #358 Cyclic numbers || solutions
- Problem #359 Hilbert's New Hotel || solutions
- Problem #360 Scary Sphere || solutions
- Problem #361 Subsequence of Thue-Morse sequence || solutions
- Problem #362 Squarefree factors || solutions
- Problem #363 Bézier Curves || solutions
- Problem #364 Comfortable distance || solutions
- Problem #365 A huge binomial coefficient || solutions
- Problem #366 Stone Game III || solutions
- Problem #367 Bozo sort || solutions
- Problem #368 A Kempner-like series || solutions
- Problem #369 Badugi || solutions
- Problem #370 Geometric triangles || solutions
- Problem #371 Licence plates || solutions
- Problem #372 Pencils of rays || solutions
- Problem #373 Circumscribed Circles || solutions
- Problem #374 Maximum Integer Partition Product || solutions
- Problem #375 Minimum of subsequences || solutions
- Problem #376 Nontransitive sets of dice || solutions
- Problem #377 Sum of digits, experience 13 || solutions
- Problem #378 Triangle Triples || solutions
- Problem #379 Least common multiple count || solutions
- Problem #380 Amazing Mazes! || solutions
- Problem #381 (prime-k) factorial || solutions
- Problem #382 Generating polygons || solutions
- Problem #383 Divisibility comparison between factorials || solutions
- Problem #384 Rudin-Shapiro sequence || solutions
- Problem #385 Ellipses inside triangles || solutions
- Problem #386 Maximum length of an antichain || solutions
- Problem #387 Harshad Numbers || solutions
- Problem #388 Distinct Lines || solutions
- Problem #389 Platonic Dice || solutions
- Problem #390 Triangles with non rational sides and integral area || solutions
- Problem #391 Hopping Game || solutions
- Problem #392 Enmeshed unit circle || solutions
- Problem #393 Migrating ants || solutions
- Problem #394 Eating pie || solutions
- Problem #395 Pythagorean tree || solutions
- Problem #396 Weak Goodstein sequence || solutions
- Problem #397 Triangle on parabola || solutions
- Problem #398 Cutting rope || solutions
- Problem #399 Squarefree Fibonacci Numbers || solutions
- Problem #400 Fibonacci tree game || solutions
- Problem #401 Sum of squares of divisors || solutions
- Problem #402 Integer-valued polynomials || solutions
- Problem #403 Lattice points enclosed by parabola and line || solutions
- Problem #404 Crisscross Ellipses || solutions
- Problem #405 A rectangular tiling || solutions
- Problem #406 Guessing Game || solutions
- Problem #407 Idempotents || solutions
- Problem #408 Admissible paths through a grid || solutions
- Problem #409 Nim Extreme || solutions
- Problem #410 Circle and tangent line || solutions
- Problem #411 Uphill paths || solutions
- Problem #412 Gnomon numbering || solutions
- Problem #413 One-child Numbers || solutions
- Problem #414 Kaprekar constant || solutions
- Problem #415 Titanic sets || solutions
- Problem #416 A frog's trip || solutions
- Problem #417 Reciprocal cycles II || solutions
- Problem #418 Factorisation triples || solutions
- Problem #419 Look and say sequence || solutions
- Problem #420 2x2 positive integer matrix || solutions
- Problem #421 Prime factors of n15+1 || solutions
- Problem #422 Sequence of points on a hyperbola || solutions
- Problem #423 Consecutive die throws || solutions
- Problem #424 Kakuro || solutions
- Problem #425 Prime connection || solutions
- Problem #426 Box-ball system || solutions
- Problem #427 n-sequences || solutions
- Problem #428 Necklace of circles || solutions
- Problem #429 Sum of squares of unitary divisors || solutions
- Problem #430 Range flips || solutions
- Problem #431 Square Space Silo || solutions
- Problem #432 Totient sum || solutions
- Problem #433 Steps in Euclid's algorithm || solutions
- Problem #434 Rigid graphs || solutions
- Problem #435 Polynomials of Fibonacci numbers || solutions
- Problem #436 Unfair wager || solutions
- Problem #437 Fibonacci primitive roots || solutions
- Problem #438 Integer part of polynomial equation's solutions || solutions
- Problem #439 Sum of sum of divisors || solutions
- Problem #440 GCD and Tiling || solutions
- Problem #441 The inverse summation of coprime couples || solutions
- Problem #442 Eleven-free integers || solutions
- Problem #443 GCD sequence || solutions
- Problem #444 The Roundtable Lottery || solutions
- Problem #445 Retractions A || solutions
- Problem #446 Retractions B || solutions
- Problem #447 Retractions C || solutions
- Problem #448 Average least common multiple || solutions
- Problem #449 Chocolate covered candy || solutions
- Problem #450 Hypocycloid and Lattice points || solutions
- Problem #451 Modular inverses || solutions
- Problem #452 Long Products || solutions
- Problem #453 Lattice Quadrilaterals || solutions
- Problem #454 Diophantine reciprocals III || solutions
- Problem #455 Powers With Trailing Digits || solutions
- Problem #456 Triangles containing the origin II || solutions
- Problem #457 A polynomial modulo the square of a prime || solutions
- Problem #458 Permutations of Project || solutions
- Problem #459 Flipping game || solutions
- Problem #460 An ant on the move || solutions
- Problem #461 Almost Pi || solutions
- Problem #462 Permutation of 3-smooth numbers || solutions
- Problem #463 A weird recurrence relation || solutions
- Problem #464 Möbius function and intervals || solutions
- Problem #465 Polar polygons || solutions
- Problem #466 Distinct terms in a multiplication table || solutions
- Problem #467 Superinteger || solutions
- Problem #468 Smooth divisors of binomial coefficients || solutions
- Problem #469 Empty chairs || solutions
- Problem #470 Super Ramvok || solutions
- Problem #471 Triangle inscribed in ellipse || solutions
- Problem #472 Comfortable Distance II || solutions
- Problem #473 Phigital number base || solutions
- Problem #474 Last digits of divisors || solutions
- Problem #475 Music festival || solutions
- Problem #476 Circle Packing II || solutions
- Problem #477 Number Sequence Game || solutions
- Problem #478 Mixtures || solutions
- Problem #479 Roots on the Rise || solutions
- Problem #480 The Last Question || solutions
- Problem #481 Chef Showdown || solutions
- Problem #482 The incenter of a triangle || solutions
- Problem #483 Repeated permutation || solutions
- Problem #484 Arithmetic Derivative || solutions
- Problem #485 Maximum number of divisors || solutions
- Problem #486 Palindrome-containing strings || solutions
- Problem #487 Sums of power sums || solutions
- Problem #488 Unbalanced Nim || solutions
- Problem #489 Common factors between two sequences || solutions
- Problem #490 Jumping frog || solutions
- Problem #491 Double pandigital number divisible by 11 || solutions
- Problem #492 Exploding sequence || solutions
- Problem #493 Under The Rainbow || solutions
- Problem #494 Collatz prefix families || solutions
- Problem #495 Writing n as the product of k distinct positive integers || solutions
- Problem #496 Incenter and circumcenter of triangle || solutions
- Problem #497 Drunken Tower of Hanoi || solutions
- Problem #498 Remainder of polynomial division || solutions
- Problem #499 St. Petersburg Lottery || solutions
- Problem #500 Problem 500!!! || solutions
- Problem #501 Eight Divisors || solutions
- Problem #502 Counting Castles || solutions
- Problem #503 Compromise or persist || solutions
- Problem #504 Square on the Inside || solutions
- Problem #505 Bidirectional Recurrence || solutions
- Problem #506 Clock sequence || solutions
- Problem #507 Shortest Lattice Vector || solutions
- Problem #508 Integers in base i-1 || solutions
- Problem #509 Divisor Nim || solutions
- Problem #510 Tangent Circles || solutions
- Problem #511 Sequences with nice divisibility properties || solutions
- Problem #512 Sums of totients of powers || solutions
- Problem #513 Integral median || solutions
- Problem #514 Geoboard Shapes || solutions
- Problem #515 Dissonant Numbers || solutions
- Problem #516 5-smooth totients || solutions
- Problem #517 A real recursion || solutions
- Problem #518 Prime triples and geometric sequences || solutions
- Problem #519 Tricolored Coin Fountains || solutions
- Problem #520 Simbers || solutions
- Problem #521 Smallest prime factor || solutions
- Problem #522 Hilbert's Blackout || solutions
- Problem #523 First Sort I || solutions
- Problem #524 First Sort II || solutions
- Problem #525 Rolling Ellipse || solutions
- Problem #526 Largest prime factors of consecutive numbers || solutions
- Problem #527 Randomized Binary Search || solutions
- Problem #528 Constrained Sums || solutions
- Problem #529 10-substrings || solutions
- Problem #530 GCD of Divisors || solutions
- Problem #531 Chinese leftovers || solutions
- Problem #532 Nanobots on Geodesics || solutions
- Problem #533 Minimum values of the Carmichael function || solutions
- Problem #534 Weak Queens || solutions
- Problem #535 Fractal Sequence || solutions
- Problem #536 Modulo power identity || solutions
- Problem #537 Counting tuples || solutions
- Problem #538 Maximum quadrilaterals || solutions
- Problem #539 Odd elimination || solutions
- Problem #540 Counting primitive Pythagorean triples || solutions
- Problem #541 Divisibility of Harmonic Number Denominators || solutions
- Problem #542 Geometric Progression with Maximum Sum || solutions
- Problem #543 Prime-Sum Numbers || solutions
- Problem #544 Chromatic Conundrum || solutions
- Problem #545 Faulhaber's Formulas || solutions
- Problem #546 The Floor's Revenge || solutions
- Problem #547 Distance of random points within hollow square laminae || solutions
- Problem #548 Gozinta Chains || solutions
- Problem #549 Divisibility of factorials || solutions
- Problem #550 Divisor game || solutions
- Problem #551 Sum of digits sequence || solutions
- Problem #552 Chinese leftovers II || solutions
- Problem #553 Power sets of power sets || solutions
- Problem #554 Centaurs on a chess board || solutions
- Problem #555 McCarthy 91 function || solutions
- Problem #556 Squarefree Gaussian Integers || solutions
- Problem #557 Cutting triangles || solutions
- Problem #558 Irrational base || solutions
- Problem #559 Permuted Matrices || solutions
- Problem #560 Coprime Nim || solutions
- Problem #561 Divisor Pairs || solutions
- Problem #562 Maximal perimeter || solutions
- Problem #563 Robot Welders || solutions
- Problem #564 Maximal polygons || solutions
- Problem #565 Divisibility of sum of divisors || solutions
- Problem #566 Cake Icing Puzzle || solutions
- Problem #567 Reciprocal games I || solutions
- Problem #568 Reciprocal games II || solutions
- Problem #569 Prime Mountain Range || solutions
- Problem #570 Snowflakes || solutions
- Problem #571 Super Pandigital Numbers || solutions
- Problem #572 Idempotent matrices || solutions
- Problem #573 Unfair race || solutions
- Problem #574 Verifying Primes || solutions
- Problem #575 Wandering Robots || solutions
- Problem #576 Irrational jumps || solutions
- Problem #577 Counting hexagons || solutions
- Problem #578 Integers with decreasing prime powers || solutions
- Problem #579 Lattice points in lattice cubes || solutions
- Problem #580 Squarefree Hilbert numbers || solutions
- Problem #581 47-smooth triangular numbers || solutions
- Problem #582 Nearly isosceles 120 degree triangles || solutions
- Problem #583 Heron Envelopes || solutions
- Problem #584 Birthday Problem Revisited || solutions
- Problem #585 Nested square roots || solutions
- Problem #586 Binary Quadratic Form || solutions
- Problem #587 Concave triangle || solutions
- Problem #588 Quintinomial coefficients || solutions
- Problem #589 Poohsticks Marathon || solutions
- Problem #590 Sets with a given Least Common Multiple || solutions
- Problem #591 Best Approximations by Quadratic Integers || solutions
- Problem #592 Factorial trailing digits 2 || solutions
- Problem #593 Fleeting Medians || solutions
- Problem #594 Rhombus Tilings || solutions
- Problem #595 Incremental Random Sort || solutions
- Problem #596 Number of lattice points in a hyperball || solutions
- Problem #597 Torpids || solutions
- Problem #598 Split Divisibilities || solutions
- Problem #599 Distinct Colourings of a Rubik's Cube || solutions
- Problem #600 Integer sided equiangular hexagons || solutions
- Problem #601 Divisibility streaks || solutions
- Problem #602 Product of Head Counts || solutions