```cpp
#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll fun(ll n)
{
if(n==0 || n==1) return 1;
return fun(n-1)*(4*n-2)/(n+1);
}
int main()
{
ll n;
cin>>n;
cout<<fun(n);
return 0;
}
```
记得开 `long long`,不然乘法的时候可能爆了 `int`(虽然除法除回了 `int`)。
@[yeyixiao2012](/user/986544)
by 2021zjhs005 @ 2023-11-20 18:47:04
@[2021zjhs005](/user/1121995)
三克油
by yeyixiao2012 @ 2023-11-20 18:55:29
@[2021zjhs005](/user/1121995) 我学会了
by lzbyyds @ 2023-12-23 13:54:41