A387474 Numbers k such that (32^k + 3^k)/35 is prime.

3, 47, 107, 157, 4799, 21841

Offset

1,1

Comments

The definition implies that k must be a prime.

a(7) > 10^5.

Links

Table of n, a(n) for n=1..6.

P. Bourdelais, A Generalized Repunit Conjecture.

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.

H. Lifchitz, Mersenne and Fermat primes field

Eric Weisstein's World of Mathematics, Repunit.

OEIS Wiki, Primes of the form (a^n+b^n)/(a+b) and (a^n-b^n)/(a-b)

Mathematica

Select[Prime[Range[10000]], PrimeQ[(32^# + 3^#)/35] &]

Crossrefs

Cf. A057187, A057188, A062587, A062589, A127996, A127997, A128344, A204940, A217320, A225807, A228922, A229542, A375161, A375236, A377031, A377856.

Sequence in context: A055058 A139845 A084295 * A141850 A003551 A054643

Adjacent sequences: A387471 A387472 A387473 * A387475 A387476 A387477

Keyword

nonn,hard,more,changed

Author

Robert Price, Aug 30 2025

Status

approved