本帖最后由 〇〇 于 2012-1-2 11:50 编辑
Problem 357
05 November 2011
Consider the divisors of 30: 1,2,3,5,6,10,15,30.
It can be seen that for every divisor d of 30, d+30/d is prime.
Find the sum of all positive integers n not exceeding 100 000 000
such that for every divisor d of n, d+n/d is prime.
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