#include<stdio.h>
int main(){
int m,i,n,a[21];
a[0]=0;a[1]=3;a[2]=7;
scanf("%d",&m);
while(m--){
scanf("%d",&n);
for(i=3;i<=n;i++){
a[i]=2*a[i-1]+a[i-2];}
printf("%d\n",a[n]);}
return 0;
}