C :

int num(int n)
{
  if(n==1) return 1;
  else return 2*(num(n-1)+1);
}
int main(int argc, char* argv[])
{
	int n;
	while(~scanf("%d",&n))
	{
	  printf("%d\n",num(n));
	}
	return 0;
}

C++ :

#include <iostream>
using namespace std;
int main()
{	
	int n,x=1;
	cin>>n;
	while(--n)
	{
		x=(x+1)*2;
	}
	cout<<x<<endl;
	return 0;
}

Pascal :

program p(input,output);
 var
 n,t,i:integer;
 a: array[1..30] of longint;
begin
 //readln(n);
 //while n>0 do
 //begin
  readln(t);
  a[t]:=1;
  for i:= t-1 downto 1 do
   a[i]:=(a[i+1]+1)*2;
  writeln(a[1]);
  dec(n);
 //end;
end.

Java :

import java.util.*;
public class Main {
public static void main(String[] args) {
   Scanner num = new Scanner(System.in);
   int N=num.nextInt();
   int lastdayNum = 1;
   for(int i=2; i<=N; i++) {
    lastdayNum = (lastdayNum+1) * 2;
   }
   System.out.println(lastdayNum);
}
}