题解 | #统计字符#
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include<stdio.h>
int fun(int n)
{
return 3*n -1;
}
int main()
{
int n;
while(EOF != scanf("%d",&n))
{
int sum=0;
for(int i=1;i<=n;i++)
{
sum += fun(i);
}
printf("%d\n",sum);
}
return 0;
}