题解 | #等差数列#
等差数列
http://www.nowcoder.com/practice/f792cb014ed0474fb8f53389e7d9c07f
递归
#include <stdio.h> #include <stdlib.h> int fun(int n){ if(n==1) return 2; return fun(n-1)+3*n-1; } int main(){ int n1,n2; int ans1,ans2; scanf("%d",&n1); ans1=fun(n1); scanf("%d",&n2); ans2=fun(n2); printf("%d\n%d",ans1,ans2); return 0; }