摘要:
https://www.51nod.com/onlineJudge/questionCode.html#!problemId=1239 51nod 1239 欧拉函数之和 https://www.51nod.com/onlineJudge/questionCode.html#!problemId=1 阅读全文
摘要:
http://www.lydsy.com/JudgeOnline/problem.php?id=4407 阅读全文
摘要:
http://www.lydsy.com/JudgeOnline/problem.php?id=4804 可以反演成Σ(i=1,n)(Σ(j,j|i)μ(j)*Φ(i/j))*[n/i]*[n/i] 过程略 设f(i)=Σ(j,j|i)μ(j)*Φ(i/j) f就是μ和Φ的卷积 μ,Φ都是积性函数 阅读全文