/archives/181/ zh-CN ###Description ![fa(1).jpg][1] ###Solution $$\sum_i^n\sum_j^m[\mu(gcd(i,j))\neq 0]lcm(i,j)$$ $$=... Thu, 01 Jan 1970 08:00:00 +0800 Thu, 01 Jan 1970 08:00:00 +0800