OFFSET
1,1
COMMENTS
a(20) > 10^5.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[7^# - 6^(# - 1)] &]
PROG
(PARI) is(n)=ispseudoprime(7^n-6^(n-1)) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, May 23 2016
STATUS
approved