Solutions to various problems from projecteuler.net.
- Go
- Julia
- 026 Reciprocal cycles
- 068 Magic 5-gon ring
- 074 Digit factorial chains
- 075 Singular integer right triangles
- 078 Coin partitions
- 078 Coin partitions (rec)
- 087 Prime power triples
- 092 Square digit chains
- 096 Su Doku
- 096 Su Doku (v2)
- 125 Palindromic sums
- 132 Large repunit factors
- 132 Large repunit factors (v2)
- 133 Repunit nonfactors
- 133 Repunit nonfactors (v2)
- 191 Prize Strings
- 191 Prize Strings (v2)
- 225 Tribonacci non-divisors
- 288 An enormous factorial
- 348 Sum of a square and a cube
- 417 Reciprocal cycles II
- 485 Maximum number of divisors
- 512 Sums of totients of powers
- 516 5-smooth totients
- 565 Divisibility of sum of divisors
- 581 47-smooth triangular numbers
- 622 Riffle Shuffles
- 675 2 to omega of n
- 719 Number Splitting
- 757 Stealthy Numbers
- PARI GP
- Perl
- 011 Largest product in a grid
- 014 Longest Collatz sequence
- 018 Maximum path sum I
- 023 Non-abundant sums
- 023 Non-abundant sums (v2)
- 027 Quadratic primes
- 030 Digit fifth powers
- 030 Digit fifth powers (v2)
- 037 Truncatable primes
- 039 Integer right triangles
- 040 Champernowne's constant
- 041 Pandigital prime
- 043 Sub-string divisibility
- 044 Pentagon numbers
- 047 Distinct primes factors
- 048 Self powers
- 049 Prime permutations
- 050 Consecutive prime sum
- 050 Consecutive prime sum (v2)
- 051 Prime digit replacements
- 051 Prime digit replacements (v2)
- 054 Poker hands
- 057 Square root convergents
- 058 Spiral primes
- 060 Prime pair sets
- 060 Prime pair sets (v2)
- 061 Cyclical figurate numbers
- 062 Cubic permutations
- 062 Cubic permutations (v2)
- 063 Powerful digit counts
- 064 Odd period square roots
- 066 Diophantine equation
- 067 Maximum path sum II
- 068 Magic 5-gon ring
- 069 Totient maximum
- 070 Totient permutation
- 070 Totient permutation (v2)
- 072 Counting fractions
- 072 Counting fractions (v2)
- 073 Counting fractions in a range
- 073 Counting fractions in a range (comb)
- 074 Digit factorial chains
- 075 Singular integer right triangles
- 076 Counting summations
- 077 Prime summations
- 077 Prime summations (unoptimized)
- 078 Coin partitions
- 078 Coin partitions (rec)
- 079 Passcode derivation
- 081 Path sum two ways
- 082 Path sum three ways
- 083 Path sum four ways
- 085 Counting rectangles
- 087 Prime power triples
- 092 Square digit chains
- 092 Square digit chains (v2)
- 093 Arithmetic expressions
- 094 Almost equilateral triangles
- 095 Amicable chains
- 096 Su Doku
- 096 Su Doku (v2)
- 098 Anagramic squares
- 099 Largest exponential
- 100 Arranged probability
- 102 Triangle containment
- 102 Triangle containment (v2)
- 104 Pandigital Fibonacci ends
- 108 Diophantine reciprocals I
- 110 Diophantine reciprocals II
- 110 Diophantine reciprocals II (oeis)
- 111 Primes with runs (v2)
- 112 Bouncy numbers
- 118 Pandigital prime sets
- 119 Digit power sum
- 123 Prime square remainders
- 124 Ordered radicals
- 127 abc-hits
- 129 Repunit divisibility
- 130 Composites with prime repunit property
- 130 Composites with prime repunit property (v2)
- 131 Prime cube partnership
- 132 Large repunit factors
- 132 Large repunit factors (v2)
- 133 Repunit nonfactors
- 133 Repunit nonfactors (v2)
- 134 Prime pair connection
- 135 Same differences
- 136 Singleton difference
- 138 Special isosceles triangles
- 142 Perfect Square Collection
- 145 How many reversible numbers are there below one-billion
- 146 Investigating a Prime Pattern
- 160 Factorial trailing digits
- 169 Exploring the number of different ways a number can be expressed as a sum of powers of 2
- 173 Using up to one million tiles how many different hollow square laminae can be formed
- 174 Counting the number of hollow square laminae that can form one two three distinct arrangements
- 179 Consecutive positive divisors
- 182 RSA encryption
- 182 RSA encryption (v2)
- 183 Maximum product of parts
- 183 Maximum product of parts (v2)
- 187 Semiprimes
- 187 Semiprimes (v2)
- 191 Prize Strings
- 192 Best Approximations
- 193 Squarefree Numbers
- 193 Squarefree Numbers (v2)
- 196 Prime triplets
- 197 Investigating the behaviour of a recursively defined sequence
- 203 Squarefree Binomial Coefficients
- 204 Generalised Hamming Numbers
- 204 Generalised Hamming Numbers (v2)
- 206 Concealed Square
- 207 Integer partition equations
- 207 Integer partition equations (v2)
- 211 Divisor Square Sum
- 211 Divisor Square Sum (oeis)
- 214 Totient Chains
- 216 Investigating the primality of numbers of the form 2
- 221 Alexandrian Integers
- 225 Tribonacci non-divisors
- 225 Tribonacci non-divisors (v2)
- 231 The prime factorisation of binomial coefficients
- 235 An Arithmetic Geometric sequence
- 243 Resilience
- 248 Numbers for which Euler's totient function equals 13
- 271 Modular Cubes part 1
- 273 Sum of Squares (v2)
- 277 A Modified Collatz sequence
- 288 An enormous factorial
- 291 Panaitopol Primes
- 293 Pseudo-Fortunate Numbers
- 303 Multiples with small digits
- 304 Primonacci
- 320 Factorials divisible by a huge integer
- 343 Fractional Sequences
- 345 Matrix Sum
- 345 Matrix Sum (v2)
- 346 Strong Repunits
- 347 Largest integer divisible by two primes
- 348 Sum of a square and a cube
- 349 Langton's ant
- 357 Prime generating integers
- 365 A huge binomial coefficient (v2)
- 365 A huge binomial coefficient (v3)
- 379 Least common multiple count
- 381 prime-k factorial
- 381 prime-k factorial (v2)
- 387 Harshad Numbers
- 401 Sum of squares of divisors
- 401 Sum of squares of divisors (v2)
- 407 Idempotents
- 407 Idempotents (v2)
- 407 Idempotents (v3)
- 417 Reciprocal cycles II
- 425 Prime connection
- 429 Sum of squares of unitary divisors
- 435 Polynomials of Fibonacci numbers
- 435 Polynomials of Fibonacci numbers (v2)
- 443 GCD sequence
- 451 Modular inverses
- 451 Modular inverses (v2)
- 479 Roots on the Rise
- 485 Maximum number of divisors
- 487 Sums of power sums
- 487 Sums of power sums (v2)
- 500 Problem 500
- 501 Eight Divisors
- 512 Sums of totients of powers
- 516 5-smooth totients
- 516 5-smooth totients (v2)
- 518 Prime Triples and Geometric Sequences
- 521 Smallest prime factor
- 521 Smallest prime factor (v2)
- 521 Smallest prime factor (v3)
- 531 Chinese leftovers
- 545 Faulhaber's Formulas
- 545 Faulhaber's Formulas (v2)
- 549 Divisibility of factorials
- 565 Divisibility of sum of divisors
- 571 Super Pandigital Numbers
- 571 Super Pandigital Numbers (v2)
- 581 47-smooth triangular numbers
- 601 Divisibility streaks
- 601 Divisibility streaks (v2)
- 609 pi sequences
- 618 Numbers with a given prime factor sum
- 621 Expressing an integer as the sum of triangular numbers
- 622 Riffle Shuffles
- 622 Riffle Shuffles (v2)
- 625 Gcd sum
- 634 Numbers of the form a^2b^3
- 634 Numbers of the form a^2b^3 (v2)
- 642 Sum of largest prime factors
- 642 Sum of largest prime factors (v2)
- 650 Divisors of Binomial Product
- 650 Divisors of Binomial Product (v2)
- 659 Largest prime
- 668 Square root smooth numbers
- 675 2 to omega of n
- 678 Fermat-like Equations
- 678 Fermat-like Equations (v2)
- 684 Inverse Digit Sum
- 686 Powers of Two
- 688 Piles of Plates
- 694 Cube-full Divisors
- 700 Eulercoin
- 700 Eulercoin (v2)
- 704 Factors of Two in Binomial Coefficients
- 708 Twos are all you need
- 719 Number Splitting
- 745 Sum of Squares
- 745 Sum of Squares (v2)
- 749 Near Power Sums
- 751 Concatenation Coincidence
- 752 Powers of 1 + sqrt(7)
- 754 Product of Gauss Factorials
- 754 Product of Gauss Factorials (v2)
- 757 Stealthy Numbers (v2)
- 784 Reciprocal Pairs (v2)
- 795 Alternating GCD Sum
- 800 Hybrid Integers
- 816 Shortest distance among points
- 820 Nth Digit of Reciprocals
- 853 Pisano Periods 1
- 853 Pisano Periods 1 (v2)
- 853 Pisano Periods 1 (v3)
- 854 Pisano Periods 2
- 932 2025
- 932 2025 (v2)
- 952 Order Modulo Factorial
- 952 Order Modulo Factorial (v2)
- Raku
- Sidef
- 001 Multiples of 3 and 5
- 001 Multiples of 3 and 5 (v2)
- 002 Even Fibonacci numbers
- 003 Largest prime factor
- 004 Largest palindrome product
- 005 Smallest multiple
- 005 Smallest multiple (v2)
- 006 Sum square difference
- 006 Sum square difference (v2)
- 007 10001st prime
- 007 10001st prime (v2)
- 007 10001st prime (v3)
- 008 Largest product in a series
- 009 Special Pythagorean triplet
- 009 Special Pythagorean triplet (v2)
- 010 Summation of primes
- 010 Summation of primes (v2)
- 011 Largest product in a grid
- 011 Largest product in a grid (v2)
- 012 Highly divisible triangular number
- 012 Highly divisible triangular number (v2)
- 013 Large sum
- 013 Large sum (v2)
- 014 Longest Collatz sequence
- 015 Lattice paths
- 016 Power digit sum
- 017 Number letter counts
- 018 Maximum path sum I
- 019 Counting Sundays
- 020 Factorial digit sum
- 021 Amicable numbers
- 021 Amicable numbers (v2)
- 022 Names scores
- 023 Non-abundant sums
- 024 Lexicographic permutations
- 024 Lexicographic permutations (v2)
- 025 1000-digit Fibonacci number
- 025 1000-digit Fibonacci number (v2)
- 025 1000-digit Fibonacci number (v3)
- 026 Reciprocal cycles
- 027 Quadratic primes
- 028 Number spiral diagonals
- 029 Distinct powers
- 030 Digit fifth powers
- 031 Coin sums
- 032 Pandigital products
- 033 Digit cancelling fractions
- 034 Digit factorials
- 035 Circular primes
- 035 Circular primes (v2)
- 036 Double-base palindromes
- 036 Double-base palindromes (v2)
- 036 Double-base palindromes (v3)
- 036 Double-base palindromes (v4)
- 037 Truncatable primes
- 038 Pandigital multiples
- 039 Integer right triangles
- 040 Champernowne's constant
- 040 Champernowne's constant (v2)
- 041 Pandigital prime
- 042 Coded triangle numbers
- 044 Pentagon numbers
- 045 Triangular pentagonal and hexagonal
- 045 Triangular pentagonal and hexagonal (v2)
- 046 Goldbach's other conjecture
- 047 Distinct primes factors
- 047 Distinct primes factors (v2)
- 048 Self powers
- 049 Prime permutations
- 050 Consecutive prime sum
- 050 Consecutive prime sum (v2)
- 051 Prime digit replacements
- 052 Permuted multiples
- 052 Permuted multiples (v2)
- 053 Combinatoric selections
- 055 Lychrel numbers
- 056 Powerful digit sum
- 057 Square root convergents
- 058 Spiral primes
- 059 XOR decryption
- 060 Prime pair sets
- 061 Cyclical figurate numbers
- 062 Cubic permutations
- 063 Powerful digit counts
- 064 Odd period square roots
- 065 Convergents of e
- 066 Diophantine equation
- 067 Maximum path sum II
- 068 Magic 5-gon ring
- 069 Totient maximum
- 070 Totient permutation
- 070 Totient permutation (v2)
- 071 Ordered fractions
- 072 Counting fractions
- 072 Counting fractions (v2)
- 073 Counting fractions in a range
- 075 Singular integer right triangles
- 075 Singular integer right triangles (v2)
- 076 Counting summations
- 077 Prime summations
- 079 Passcode derivation
- 079 Passcode derivation (v2)
- 080 Square root digital expansion
- 081 Path sum two ways
- 082 Path sum three ways
- 085 Counting rectangles
- 087 Prime power triples
- 089 Roman numerals
- 094 Almost equilateral triangles
- 095 Amicable chains
- 096 Su Doku
- 097 Large non-Mersenne prime
- 099 Largest exponential
- 100 Arranged probability
- 100 Arranged probability (v2)
- 100 Arranged probability (v3)
- 104 Pandigital Fibonacci ends
- 108 Diophantine reciprocals I
- 108 Diophantine reciprocals I (v2)
- 110 Diophantine reciprocals II
- 111 Primes with runs
- 112 Bouncy numbers
- 119 Digit power sum
- 120 Square remainders
- 123 Prime square remainders
- 124 Ordered radicals
- 125 Palindromic sums
- 129 Repunit divisibility
- 130 Composites with prime repunit property
- 130 Composites with prime repunit property (v2)
- 131 Prime cube partnership
- 132 Large repunit factors
- 133 Repunit nonfactors
- 134 Prime pair connection
- 137 Fibonacci golden nuggets
- 138 Special isosceles triangles
- 140 Modified Fibonacci golden nuggets
- 140 Modified Fibonacci golden nuggets (v2)
- 142 Perfect Square Collection
- 169 Exploring the number of different ways a number can be expressed as a sum of powers of 2
- 169 Exploring the number of different ways a number can be expressed as a sum of powers of 2 (v2)
- 173 Using up to one million tiles how many different hollow square laminae can be formed
- 174 Counting the number of hollow square laminae that can form one two three distinct arrangements
- 182 RSA encryption
- 183 Maximum product of parts
- 187 Semiprimes
- 188 The hyperexponentiation of a number
- 191 Prize Strings
- 193 Squarefree Numbers
- 197 Investigating the behaviour of a recursively defined sequence
- 203 Squarefree Binomial Coefficients
- 204 Generalised Hamming Numbers
- 206 Concealed Square
- 231 The prime factorisation of binomial coefficients
- 235 An Arithmetic Geometric sequence
- 248 Numbers for which Euler's totient function equals 13
- 271 Modular Cubes part 1
- 277 A Modified Collatz sequence
- 293 Pseudo-Fortunate Numbers
- 345 Matrix Sum
- 346 Strong Repunits
- 381 prime-k factorial
- 387 Harshad Numbers
- 435 Polynomials of Fibonacci numbers
- 443 GCD sequence
- 463 A weird recurrence relation
- 479 Roots on the Rise
- 493 Under the Rainbow
- 500 Problem 500
- 501 Eight Divisors
- 501 Eight Divisors (v2)
- 518 Prime Triples and Geometric Sequences
- 521 Smallest prime factor
- 581 47-smooth triangular numbers
- 601 Divisibility streaks
- 622 Riffle Shuffles
- 634 Numbers of the form a^2b^3
- 642 Sum of largest prime factors
- 668 Square root smooth numbers
- 684 Inverse Digit Sum
- 684 Inverse Digit Sum (v2)
- 686 Powers of Two
- 686 Powers of Two (v2)
- 688 Piles of Plates
- 694 Cube-full Divisors
- 700 Eulercoin
- 704 Factors of Two in Binomial Coefficients
- 708 Twos are all you need
- 708 Twos are all you need (v2)
- 745 Sum of Squares
- 745 Sum of Squares (v2)
- 748 Upside down Diophantine equation
- 751 Concatenation Coincidence
- 752 Powers of 1 + sqrt(7)
- 784 Reciprocal Pairs
- 800 Hybrid Integers
- 808 Reversible prime squares
- 816 Shortest distance among points
- 836 A Bold Proposition
- 853 Pisano Periods 1
- 854 Pisano Periods 2
- 854 Pisano Periods 2 (v2)
- 918 Recursive Sequence Summation
- 932 2025