打表 + 数组运用

#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	int a[31] = {0,1,2,4,7,12,21,37,65,114,200,351,616,1081,1897,3329,5842,10252,17991,31572,55405,97229,170625,299426,525426,922111,1618192,2839729,4983377,8745217,15346786};
	cout<<a[n];
	return 0;
}