OFFSET
1,1
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
PROG
(PARI) is(n)=ispseudoprime(20^n-19^n) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
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