OFFSET
1,1
LINKS
Harvey Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.
Henri Lifchitz, Mersenne and Fermat primes field
MATHEMATICA
Select[Prime[Range[100000]], PrimeQ[(39^#-1)/38]&]
PROG
(PARI) is(n)=ispseudoprime((39^n-1)/38) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Robert Price, Apr 04 2012
STATUS
approved