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Encyclopedia > Cuban prime

A cuban prime is a prime number that is a solution to one of two different specific equations involving third powers of x and y. The first of these equations is


p = (x3 - y3) / (x - y),x = y + 1,y > 0


and the first few cuban primes from this equation are


7, 19, 37, 61, 127, 271, 331, 397, 547, 631, 919, 1657, 1801, 1951, 2269, 2437, 2791, 3169, 3571, 4219, 4447, 5167, 5419, 6211, 7057, 7351, 8269, 9241, 10267, 11719, 12097, 13267, 13669, 16651, 19441, 19927, 22447, 23497, 24571, 25117, 26227


The general cuban prime of this kind can be rewritten as ((y+1)3 - y3) / (y + 1 - y), which simplifies to 3y2 + 3y + 1. This is exactly the general form of a centered hexagonal number; that is, all of these cuban primes are centered hexagonal.


This kind of cuban primes has been researched by A. J. C. Cunningham, in a paper entitled On quasi-Mersennian numbers.


The second of these equations is


p = (x3 - y3) / (x - y),x = y + 2


and the first few cuban primes from this equation are


13, 109, 193, 433, 769, 1201, 1453, 2029, 3469, 3889, 4801, 10093, 12289, 13873, 18253, 20173, 21169, 22189, 28813, 37633, 43201, 47629, 60493, 63949, 65713, 69313


This kind of cuban primes have also been researched by Cunningham, in his book Binomial Factorisations.


The name "cuban prime" has to do with the role cubes (third powers) play in the equations, and has nothing to do with prime Cuban cigars or with Cuban prime minister Fidel Castro.


  Results from FactBites:
 
Index to On-Line Encyclopedia of Integer Sequences (1610 words)
primes, by primitive root: (02) A019336 A019337 A019338 A019339 A019340 A019341 A019342 A019343 A019344 A019345 A019346 A019347
Primes, consecutive, A006549, A007700, A007513, A007529, A007530, A006489
Primes, primitive roots of, A001918, A002233, A002199, A002231, A001122, A007348, A003147, A001913, A001123, A007349, A001124, A001125, A001126
Cuban prime - Wikipedia, the free encyclopedia (268 words)
A cuban prime is a prime number that is a solution to one of two different specific equations involving third powers of x and y.
This is exactly the general form of a centered hexagonal number; that is, all of these cuban primes are centered hexagonal.
The name "cuban prime" has to do with the role cubes (third powers) play in the equations, and has nothing to do with Cuba.
  More results at FactBites »


 

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