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  1. #include <stdio.h>
  2.  
  3. char isMersenneLucasLehmer(unsigned long int prime)
  4. {
  5.     unsigned long long int i, termN = 4;
  6.     unsigned long mersenne;
  7.     unsigned int limit;
  8.     int res;
  9.  
  10.     mersenne = (unsigned long) pow(2, (double)prime) - 1;
  11.     if (prime % 2 == 0)
  12.     {
  13.         return prime == 2;
  14.     }
  15.     else 
  16.     {
  17.         res = (int)sqrt((double) prime);
  18.         for (i = 3; i <= res; i += 2)
  19.         {
  20.             if (prime % i == 0)
  21.             {
  22.                 return 0;  
  23.             }
  24.         }
  25.  
  26.         limit = prime - 2;
  27.         for (i = 1; i <= limit; ++i)
  28.         {
  29.             termN = (termN * termN - 2) % mersenne;
  30.  
  31.         }
  32.     }
  33.     return termN == 0;
  34. }
  35. //----------------------------------------------------------
  36.  
  37. /*
  38.     Function: findMersenneLucasLehmer()
  39.  
  40. */
  41. void findMersenneLucasLehmer(unsigned int limit)
  42. {
  43.     unsigned int i, current = 0;
  44.     unsigned long mersenne, bitsInLong = 64;
  45.  
  46.     for (i = 2; i <= bitsInLong; i++)
  47.     {
  48.         if (current >= limit)
  49.         {
  50.             break;
  51.         }
  52.  
  53.  
  54.         if (isMersenneLucasLehmer(i))   
  55.         {
  56.             mersenne = (unsigned long) pow(2, (double)i) - 1;
  57.             printf("current = %lu, mersenne = %lu, index = %u\n", current, mersenne, i);
  58.             ++current;
  59.         } 
  60.     }
  61. }
  62.  
  63. int main(void) {
  64. 	printf("Size of unsigned long: %d\n", sizeof (unsigned long));
  65. 	printf("Size of unsigned long long: %d\n\n", sizeof (unsigned long long));
  66. 	findMersenneLucasLehmer(8);
  67. 	return 0;
  68. }
  69.  
Success #stdin #stdout 0s 2168KB
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stdin
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Standard input is empty
stdout
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Size of unsigned long: 4
Size of unsigned long long: 8

current = 0, mersenne = 3, index = 2
current = 1, mersenne = 7, index = 3
current = 2, mersenne = 31, index = 5
current = 3, mersenne = 127, index = 7
current = 4, mersenne = 8191, index = 13
current = 5, mersenne = 131071, index = 17
current = 6, mersenne = 524287, index = 19
current = 7, mersenne = 2147483647, index = 31
https://ideone.com/Whmqur
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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