GCD
定理:与n互质的i的和为n*phi(n)/2(n>2)
http://blog.csdn.net/willinglive/article/details/39619427
添加:
http://blog.sina.com.cn/s/blog_71ded6bf0100sxwu.html
排列组合
http://wenku.baidu.com/link?url=NI7VLiYn8o46r8OGGfzFa-HdW_oDVg7ARzPpj9FvELL_ZTcXu0tXkgp_kPpRn_nrG2s2nNrUGXTactWWyFiwj9b2bmp4dnDNDmu2sEQkLYm
算法导论数论部分