OFFSET
1,1
COMMENTS
PrimePi[ a(n) ] = {2, 253, 287, 1331, ...}. - Alexander Adamchuk, Feb 16 2007
a(5) > 10^5. - Robert Price, Jun 05 2012
Terms greater than 1000 may correspond to (unproven) strong pseudoprimes. - M. F. Hasler, Sep 16 2013
PROG
(PARI) is(n)=ispseudoprime(19^n-18^n) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Mike Oakes, May 18 2001, May 19 2001
EXTENSIONS
10957 (found by Mike Oakes in 2003) from Alexander Adamchuk, Feb 16 2007
STATUS
approved