HDU 1023 Train Problem II

import java.io.*;
import java.math.*;
import java.util.*;
import java.text.*;
public class Main
{
public static void main(String[] args)
{
Scanner cin=new Scanner (new BufferedInputStream(System.in));
BigInteger[] f=new BigInteger[103];
f[0]=f[1]=f[2]=BigInteger.valueOf(1);
for(int i=2;i<102;i++)
f[i+1]=BigInteger.valueOf(4).multiply(BigInteger.valueOf(i)).subtract(BigInteger.valueOf(6)).multiply(f[i]).divide(BigInteger.valueOf(i));
while(cin.hasNext())
{
int n=cin.nextInt();
System.out.println(f[n+2]);
}
}
}