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;
}
