题解 | #等差数列#
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include<stdio.h>
int main()
{
int n;
int sum;
scanf("%d", &n);
sum = 2*n + n*(n-1)*3/2;
printf("%d", sum);
return 0;
}
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include<stdio.h>
int main()
{
int n;
int sum;
scanf("%d", &n);
sum = 2*n + n*(n-1)*3/2;
printf("%d", sum);
return 0;
}
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