摘要：题意:求$$\sum_{i=1}^{n}\sum_{j=1}^{m}[gcd(i,j) = prim]$$ 题解:那就开始化式子吧!! $$f(d) = \sum_{i=1}^{n}\sum_{j=1}^{m}[gcd(i,j) = d]$$ $$F(x) = \sum_{d|x} f(d) = \ 阅读全文