1,1

All terms are primes.

J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

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

Eric Weisstein's World of Mathematics, Repunit.

H. Lifchitz, Mersenne and Fermat primes field

Do[ p=Prime[n]; If[ PrimeQ[ (31^p + 1)/32 ], Print[p] ], {n, 1, 1100} ]

Cf. A000978 = numbers n such that (2^n + 1)/3 is prime. Cf. A007658, A057171, A057172, A057173, A057175, A001562, A057177, A057178, A057179, A057180, A057181, A057182, A057183, A057184, A057185, A057186, A057187, A057188, A057189, A057190, A057191, A071380, A071381, A071382. Cf. A084741, A084742, A065507, A126659.

Sequence in context: A166560 A139644 A142640 this_sequence A142915 A142366 A103734

Adjacent sequences: A126853 A126854 A126855 this_sequence A126857 A126858 A126859

bref,hard,more,nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Mar 23 2007