括号序列。
by Register_int @ 2023-08-24 12:13:42
@[Register_int](/user/406941) orz
by lqyc @ 2023-08-24 12:14:31
@[Register_int](/user/406941) ~~是什么，能将详细点吗 & orz~~
by CSP_juruo @ 2023-08-24 12:15:10
此贴结，~~还有想法的可以说~~
by CSP_juruo @ 2023-08-24 12:21:49
就是卡特兰数啊...
推销一下个人blog:[卡特兰数](https://www.cnblogs.com/SXqwq/p/17689682.html)
by SXqwq @ 2023-09-16 08:16:04
这么证明：
```cpp
long long ans[18]={1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845,35357670,129644790,477638700};
```
关于递推式：
```cpp
#include <bits/stdc++.h>
using namespace std;
long long katelan(int n){
if(n==0||n==1){
return 1;
}
long long sum=0;
for(int i=1;i<=n;i++){
sum+=katelan(i-1)*katelan(n-i);
}
return sum;
}
int main(){
cout<<"ans={";
for(int n=1;n<=18;n++)cout<<katelan(n)<<(n==18?"};":",");
return 0;
}
```
by YuanShenYYD @ 2023-10-16 19:59:21
看这个
https://zhuanlan.zhihu.com/p/97619085#%E4%BA%8C%E3%80%81%E7%BB%8F%E5%85%B8%E9%97%AE%E9%A2%98
by baen @ 2023-10-26 14:54:02