A062586 Numbers k such that 20^k - 19^k is prime.

5, 17, 109, 1979, 6899, 7331, 18661, 79621, 81649

Offset: 1

Author

Mike Oakes, May 18 2001, May 19 2001

Keywords

• nonn
• hard

Comments

Terms k > 1000 may correspond to (unproven) strong pseudoprimes.

Links

• Henri Lifchitz and Renaud Lifchitz, Top probable primes of the form 20^p-19^p

Crossrefs

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Programs

PARI

is(n)=ispseudoprime(20^n-19^n) \\ Charles R Greathouse IV, Jun 12 2017

Extensions

a(7)-a(9) found by Jean-Louis Charton in February and March 2011

Edited by M. F. Hasler, Sep 16 2013