摘要：Reciprocal cyclesProblem 26A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denomina... 阅读全文

摘要：Quadratic primesProblem 27Euler discovered the remarkable quadratic formula:n2+n+41It turns out that the formula will produce 40 prime... 阅读全文

摘要：Pandigital prime setsProblem 118Using all of the digits 1 through 9 and concatenating them freely to form decimal integers, different ... 阅读全文

摘要：Double-base palindromesProblem 36The decimal number, 585 = 10010010012 (binary), is palindromic in both bases.Find the sum of all numb... 阅读全文

摘要：Pandigital multiplesProblem 38Take the number 192 and multiply it by each of 1, 2, and 3:192 × 1 = 192192 × 2 = 384192 × 3 = 576By con... 阅读全文

摘要：Pandigital Fibonacci endsProblem 104The Fibonacci sequence is defined by the recurrence relation:Fn = Fn−1 + Fn−2, where F1 = 1 and F2... 阅读全文

摘要：Pandigital productsProblem 32We shall say that an n-digit number is pandigital if it makes use of all the digits 1 ton exactly once; f... 阅读全文

摘要：Pandigital primeProblem 41We shall say that an n-digit number is pandigital if it makes use of all the digits 1 ton exactly once. For ... 阅读全文

摘要：Digit factorialsProblem 34145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.Find the sum of all numbers which are equal to... 阅读全文

摘要：Non-abundant sumsProblem 23A perfect number is a number for which the sum of its proper divisors is exactly equal to the number. For e... 阅读全文