qq_41997978的博客

n%d+m%d≥dn \% d + m \% d \geq dn%d+m%d≥d 可以写成 n−⌊nd⌋∗d+m−⌊md⌋∗d≥dn - \lfloor\frac{n}{d}\rfloor * d +m - \lfloor\frac{m}{d}\rfloor * d \geq dn−⌊dn​⌋∗d+m−⌊dm​⌋∗d≥d 移项一下可以得出：⌊nd⌋+⌊md⌋+1≥⌊n+md⌋\lfloor\f...

题目大意：让你求：∑i=1n∑j=1n∑k=1nϕ(i)ϕ(j2)ϕ(k3)ϕ(i)ϕ(j)ϕ(i)ϕ(gcd(i,j,k))让你求：\sum_{i = 1}^n\sum_{j = 1}^n\sum_{k = 1}^n\frac{\phi(i)\phi(j ^ 2)\phi(k^3)}{\phi(i)\phi(j)\phi(i)}\phi(gcd(i,j,k))让你求：i=1∑n​j=1∑n​...