HW5.28

 1 public class Solution
 2 {
 3     public static void main(String[] args)
 4     {
 5         System.out.printf("%s\t%s\n", "p", "2^p - 1");
 6
 7         for(int i = 2; i <= 31; i++)
 8         {
 9             if(isPrime((int)getMersenne(i)))
10                 System.out.printf("%d\t%d\n", i, (int)getMersenne(i));
11         }
12     }
13
14     public static double getMersenne(int n)
15     { return Math.pow(2, n) - 1; }
16
17     public static boolean isPrime(int n)
18     {
19         if(n == 1)
20             return false;
21         else if(n == 2)
22             return true;
23         else
24         {
25             for(int i = 2; i < n; i++)
26             {
27                 if(n % i == 0)
28                     return false;
29             }
30             return true;
31         }
32     }
33 }