Hello everyone, Today I stumbled upon a new topic called Möbius Function and i read about it both in the wiki as well as in one of the codechef editorials page. This is the problem http://www.codechef.com/problems/COPRIME3 and here is its editorial http://discuss.codechef.com/questions/46074/coprime3-editorial .

Even after i read through the editorial i still couldn't understand why the solution for this problem using Möbius function is correct and its proof. So, can anyone please give a simple explanation about the Möbius function and the various kinds of problems that can be solved with it?