Seeking a number of factors, and

Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/yangmolulu/article/details/82877949

Playing table
SUM [i] i of each factor is stored sum.
Screening

void makeTable(int n){
	memset(sum,0,sizeof(sum));
	sum[1] = 0;
	
	int i = 2,j;
	while(i <= n){
		sum[i]++;
		j = i + i;
		while(j <= n){
			sum[j] += i;
			j += i;
		}
		i++;
	}
}