题解 | #等差数列#
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
int main(void)
{
int n;
scanf("%d",&n);
printf("%d",(4+3*(n-1))*n/2);
return 0;
}
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
int main(void)
{
int n;
scanf("%d",&n);
printf("%d",(4+3*(n-1))*n/2);
return 0;
}
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