walfy

摘要： 求:$\sum_{i=1}^n\sum_{j=1}^m\mu(gcd(i,j))^2$ 化简可得$\sum_{i=1}^{min(n,m)}{\lfloor \frac{n}{i} \rfloor}{\lfloor \frac{m}{i} \rfloor}\sum_{d|i}\mu(d)^2 \mu 阅读全文