OFFSET
1,3
COMMENTS
a(18) > 10^5.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[7^# + 6^(# + 1)] &]
PROG
(Magma) [n: n in [0..500] | IsPrime(7^n+6^(n+1))]; // Vincenzo Librandi, Jul 12 2016
(PARI) is(n)=ispseudoprime(7^n+6^(n+1)) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jul 11 2016
STATUS
approved