摘要: Link 题解: $ans = \sum_{i = 1}^{n}\sum_{j = 1}^{n}phi(gcd(phi(i), phi(j)))$ $=\sum_{d = 1}^{n}phi(d)\sum_{i = 1}^{n}\sum_{j = 1}^{n}[gcd(phi(i), phi(j)) 阅读全文
posted @ 2019-09-23 19:06 WstOne 阅读(149) 评论(0) 推荐(0) 编辑