https://www.hackerrank.com/submissions/code/1543024

uthopiantree.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include <ctype.h>
int main(int argc, char const *argv[])
{
	int testc,ans,t,years,extrac;
	scanf("%d", &testc);
	while(testc--)
	{
		scanf("%d", &t);
		years=t/2;
		extrac=t%2;
		ans=pow(2,years+1)-1;
		if (extrac)
			ans*=2;
		printf("%d\n", ans);
	}
	return 0;
}