Chenjb的专栏

求Σni=1\Sigma _{i=1} ^{n}Σmj=1\Sigma_{j=1}^{m}(gcd(i,j))k(gcd(i,j))^kΣni=1\Sigma _{i=1} ^{n}Σmj=1\Sigma_{j=1}^{m}(gcd(i,j))k(gcd(i,j))^k =Σni=1=\Sigma_{i=1}^{n}Σmj=1\Sigma_{j=1}^{m}Σp/i,p/jpk\Sigma_{p/