poj 2663 Tri Tiling

Description

In how many ways can you tile a 3xn rectangle with 2x1 dominoes? 
Here is a sample tiling of a 3x12 rectangle. 

Input

Output

Sample Input

2
8
12
-1

Sample Output

3
153
2131

题解：a[i]=4*a[i-2]-a[i-4];  

#include <iostream>
using namespace std;
int main(){
	long long n,a[50];
	a[0]=1;a[2]=3; 
	for(int i=4;i<=30;i+=2)  
		a[i]=4*a[i-2]-a[i-4];  
	while (cin>>n&&n!=-1){
		if (n%2)
			cout<<0<<endl;
		else
			cout<<a[n]<<endl;
	}
	return 0;
}

poj 2663 Tri Tiling

原文：http://blog.csdn.net/codeforcer/article/details/40301431