C :

#include<stdio.h>

int main()
{
	int i,c,n,a[31],b[31],sum;
	a[1]=1;
	sum=a[1];
	for(i=2;i<=30;i++)
	{
		if(i%2==0)
		{
			a[i]=sum+2;
			sum=sum+a[i];
		}
		else
		{
			a[i]=sum+1;
			sum=sum+a[i];
		}
	}
	scanf("%d",&c);
	while(c--)
	{
		scanf("%d",&n);
		printf("%d\n",a[n]);
	}
	return 0;
}

C++ :

#include<stdio.h>

int main()
{
	int i,c,n,a[31],b[31],sum;
	a[1]=1;
	sum=a[1];
	for(i=2;i<=30;i++)
	{
		if(i%2==0)
		{
			a[i]=sum+2;
			sum=sum+a[i];
		}
		else
		{
			a[i]=sum+1;
			sum=sum+a[i];
		}
	}
	scanf("%d",&c);
	while(c--)
	{
		scanf("%d",&n);
		printf("%d\n",a[n]);
	}
	return 0;
}