题目链接P4449于神之怒加强版题目大意：求\[\sum_{i=1}^{n}\sum_{j=1}^{m}gcd(i,j)^k\]\(数据范围n,m\leq5e6\)\(二话不说，先开导式子(假定n<m)：\)\begin{aligned}ans&=\sum_{i=1}^{n}\sum_{j=1}^{m}gcd(i,j)^k\\\end{aligned}\[先套路地枚举d=gcd(i,j)\]\begin{align