OFFSET
1,1
COMMENTS
Terms > 1000 are often only strong pseudoprimes.
a(5) > 10^5. - Robert Price, Aug 12 2012.
PROG
(PARI) is(n)=ispseudoprime(27^n-26^n) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Mike Oakes, May 18 2001, May 19 2001
EXTENSIONS
a(4) from Robert Price, Aug 12 2012
STATUS
approved