题解 | #等差数列#
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include<bits/stdc++.h> using namespace std; int main(){ int n; while(~scanf("%d",&n)){ printf("%d\n",(1+3*n)*n/2); } return 0; }
等差数列
https://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
#include<bits/stdc++.h> using namespace std; int main(){ int n; while(~scanf("%d",&n)){ printf("%d\n",(1+3*n)*n/2); } return 0; }
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