/*
   Lab : Lab6
   Day : Tuesday  [ 09 Sept 08 ]

   Problem Number: 02
   Problem Title : Mersenne Prime
   
   Theory :
      The hint provided in the question is complete. 
      Let's follow the guidelines given in the hint
	
	1. Write method "isPrime" for to test a number for primarity
	2. Write method "GenerateMersenneNumber" 
           it takes a number n as input and returnes 2^n-1
	   a simple for loop will do the job
	
        
 */

class sol_lab6_prob02{

	//method "isPrime" returns 1 if number is prime, otherwise returnes 0
	public static int isPrime(long number)
	{
		long i;
		 
		for( i = 2; i*i <= number ; i = i + 1)
		{  
			if( ( number % i ) == 0 )
			{				 
				return 0;
			}
		}
  
		return 1;
	}

        //method "GenerateMersenneNumber" 
	public static long  GenerateMersenneNumber(int n)
	{
		int i;
		long two_raised_power_i;

		two_raised_power_i = 1;
		
		for ( i = 1 ; i <= n ; i = i + 1 )
		{  
			two_raised_power_i = two_raised_power_i * 2;
		} 
	
		return ( two_raised_power_i - 1 );
	}

	
   	public static void main(String args[])
	{		
		int i;		 

		System.out.println(" Mersenne Prime are ");

		for( i = 2 ; i <= 31 ; i = i + 1 )
		{ 
			if( isPrime( i ) == 1 )
			{	 
				if ( isPrime( GenerateMersenneNumber(i) ) == 1 )
				{       
					System.out.println(" " + GenerateMersenneNumber(i) + "( = 2 ^ " + i + " - 1 )" );
				}
			}
		}
			
	}	
}