题解 | #等差数列#
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include <iostream> using namespace std; int main() { int a; while (cin >> a) { // 注意 while 处理多个 case auto sum=0; for(auto i=1;i<=a;i++) { sum+=i*3-1; } cout<<sum<<endl; } } // 64 位输出请用 printf("%lld")