摘要：HDU5528 Count a b 做法：求$\sum_{m|n}(m^2 \sum_{i=1}^{m}\sum_{j=1}^m [m|(ij)])$ $h(m) = \sum_{i=1}^{m}\sum_{j=1}^m [m|(ij)] = \sum_{i=1}^m\sum_{j=1}^m [\f 阅读全文

摘要：ACM ICPC 2018 徐州赛区网络预赛 D. EasyMath 做法： $$f(m,n) = \sum _{i=1}^{m} \mu(in) = \sum_{i=1}^{m}[gcd(i,n)=1]\mu(i)\mu(n) = \mu(n)\sum_{d|n}\mu(d)f(\frac{m}{ 阅读全文