[SPOJ VLATTICE] Visible Lattice Points（莫比乌斯反演）

Description

Consider a N*N*N lattice. One corner is at (0,0,0) and the opposite one is at (N,N,N). How many lattice points are visible from corner at (0,0,0) ? A point X is visible from point Y iff no other lattice point lies on the segment joining X and Y.

Http

http://www.spoj.com/problems/VLATTICE/en/

解决思路

x==1带进去，得到最终的式子
$F(x)=\sum_{i=1}^n \mu (i) {\lfloor \frac{n}{i} \rfloor}^3$

HNCJ OIer 一枚