数列求和用循环不用递归怎么做（小白

Question

Answer 1

#include <stdio.h>
int main()
{
    int n1=1,n2=2,n3=3,i,n;
    long long sum = 0,an;
    scanf("%d",&n);
    for (i=3;i<=n;i++)
    {
        an = n1*n2*n3;
        sum += an;
        n1++;
        n2++;
        n3++;
    }
    printf("%lld",sum);
    return 0;
}