题解 | #等差数列#
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include <iostream>
using namespace std;
int main() {
int n;
cin >> n;
int a=0;
int a0 =2;
for(int i=0;i<n;i++){
a = a + a0;
a0 = a0 + 3;
}
cout << a << endl;
}
// 64 位输出请用 printf("%lld")
