A071382 Numbers n such that (30^n+1)/31 is a prime.

139, 173, 547, 829, 2087, 2719, 3109, 10159, 56543, 80599

Offset

1,1

Comments

Some of the larger terms may only correspond to probable primes.

a(11) > 10^5. - Robert Price, Jul 10 2013

Links

Table of n, a(n) for n=1..10.

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

H. Lifchitz, Mersenne and Fermat primes field

Mathematica

 Select[Range[3000], PrimeQ[(30^# + 1) / 31] &] (* Vincenzo Librandi, Oct 29 2017 *)

Prog

(PARI) isok(n) = (denominator(p=(30^n+1)/31)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017

Crossrefs

Cf. A071381.

Sequence in context: A325075 A020357 A050967 * A290450 A209618 A031928

Adjacent sequences: A071379 A071380 A071381 * A071383 A071384 A071385

Keyword

nonn,more

Author

Rick L. Shepherd, May 22 2002

Extensions

a(8) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(9)-a(10) from Robert Price, Jul 10 2013

Status

approved