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

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

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..9.

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

Prog

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

Crossrefs

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

Sequence in context: A267143 A331636 A234797 * A301641 A067710 A197912

Adjacent sequences: A062583 A062584 A062585 * A062587 A062588 A062589

Keyword

nonn,hard

Author

Mike Oakes, May 18 2001, May 19 2001

Extensions

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

Edited by M. F. Hasler, Sep 16 2013

Status

approved