HDU 2077

#include<stdio.h>
#include<math.h>

int main()
{
    long long int Hanoi[25];
    int i,n,t;
    Hanoi[2] = 4;
    Hanoi[1] = 2;
    for(i = 3;i <= 20;i ++)
    {
        Hanoi[i] = 3*(pow(3,i-2)-1) + 4;
    }
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        printf("%I64d\n",Hanoi[n]);
    }
    return 0;
}