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Problem 21 https://projecteuler.net/problem=21 Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n) 阅读全文
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Problem 34 https://projecteuler.net/problem=34 145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145. 145是一个神奇的数字，1! + 4! + 5! = 1 + 24 + 120 阅读全文
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Problem 42 https://projecteuler.net/problem=42 The nth term of the sequence of triangle numbers is given by, tn = ½n(n+1); so the first ten triangle n 阅读全文