OFFSET
1,1
COMMENTS
a(19) > 10^5.
EXAMPLE
7 is a member since 5^7 - 4^8 = 78125 - 65536 = 12589 which is a prime number.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[5^# - 4^(# + 1)] &]
PROG
(PARI) is(n)=ispseudoprime(5^n-4^(n+1)) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Apr 27 2016
STATUS
approved