https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes https://projecteuler.net/problem=10 http://www.shuizilong.com/house/archives/project-euler-521-smallest-prime-factor/ http://roosephu.github.io/2013/06/16/PE-432/ http://yhylord.logdown.com/posts/2014/04/06/linear-sieve-and-multiplicative-function ……