牛牛数列4
牛牛学数列4
http://www.nowcoder.com/questionTerminal/586b114f52034688879342ba45779081
其实就是等差数列求和而已
n有多大，就求多少次和
#include <stdio.h>
int main()
{
int n;
int sum = 0;
int i = 1;
int sign = 1;
scanf("%d",&n);
for(i=1;i<=n;i++)
{
sum += i*(1+i)/2;
}
printf("%d\n",sum);
return 0;}
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