English

Primality of numbers of the form $ap^{k}+1$

Number Theory 2021-04-13 v5

Abstract

In 1876, Edouard Lucas showed that if an integer bb exists such that bn11(mod n)b^{n-1} \equiv 1 (\mathrm{mod} \ n) and b(n1)/p≢1(mod n)b^{(n-1)/p} \not\equiv 1( \mathrm{mod} \ n) for all prime divisors pp of n1n-1 , then nn is prime, a result known as Lucas's converse of Fermat's little theorem. This result was considerably improved by Henry Pocklington in 1914 when he showed that it's not necessary to know all the prime factors of n1n-1 in order to determine if nn is prime. In this paper we optimize Pocklington's primality test for integers of the form apk+1ap^{k}+1 where pp is prime, a<pa<p, k1k\ge 1. An extension of Lucas's converse of Fermat's little theorem is given. We also prove a new general-purpose primality test that requires that only a single odd prime divisor of n1n-1 be found for the test to be implemented. Contrary to the well-known result: There are infinitely many Fermat pseudoprimes to any base bb; In this paper we prove the finitude of Fermat pseudoprimes in some forms of integers.

Keywords

Cite

@article{arxiv.2005.02327,
  title  = {Primality of numbers of the form $ap^{k}+1$},
  author = {Ariko Stephen Philemon},
  journal= {arXiv preprint arXiv:2005.02327},
  year   = {2021}
}