题目描述
Let σ0(n) be the number of positive divisors of n.
For example, σ0(1)=1 , σ0(2)=2 and σ0(6)=4.
Let S1(n)=∑i=1nσ0(i).
Given N, find S1(N).
Let $\sigma_0(n)$ be the number of positive divisors of $n$.
For example, $\sigma_0(1) = 1$ , $\sigma_0(2) = 2$ and $\sigma_0(6) = 4$.
Let $S_1(n) = \sum _{i=1}^n \sigma_0(i)$.
Given $N$, find $S_1(N)$.
