

A071380


Numbers n such that (26^n+1)/27 is a prime.


15




OFFSET

1,1


COMMENTS

Some of the larger terms may only correspond to probable primes.
a(9) > 10^5.  Robert Price, Jul 07 2013


LINKS

Table of n, a(n) for n=1..8.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.


MATHEMATICA

Select[Range[3000], PrimeQ[(26^# + 1) / 27] &] (* Vincenzo Librandi, Oct 29 2017 *)


PROG

(PARI) isok(n) = (denominator(p=(26^n+1)/27)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017


CROSSREFS

Cf. A057191, A071381.
Sequence in context: A080158 A156935 A308965 * A142423 A159495 A125423
Adjacent sequences: A071377 A071378 A071379 * A071381 A071382 A071383


KEYWORD

nonn,more


AUTHOR

Rick L. Shepherd, May 22 2002


STATUS

approved



