A071380 Numbers n such that (26^n+1)/27 is a prime.

11, 109, 227, 277, 347, 857, 2297, 9043, 501409

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..9.

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,hard,more

Author

Rick L. Shepherd, May 22 2002

Extensions

a(9) from Paul Bourdelais, Oct 02 2023

Status

approved