摘要:"题目链接" $Description$ 求$$\sum_{i=1}^n\sum_{j=1}^i\frac{lcm(i,j)}{gcd(i,j)}$$ 答案对$10^9+7$取模。 $n include include using namespace std; const int mod=1e9+7 阅读全文
posted @ 2019-03-15 10:34 LeTri 阅读(172) 评论(0) 推荐(0) 编辑