A034923 Numbers k such that 43^k - 42 is prime.

4, 6, 42, 64, 65, 1017, 3390, 3894, 8904, 12976

Offset

1,1

Comments

Related to hyperperfect numbers of a certain form.

k = 1017 produces a 1662-digit number which is only a probable prime. Any additional terms are greater than 1500.

a(7) > 3000. - Vincenzo Librandi, Sep 27 2012

a(11) > 50000. - Michael S. Branicky, Nov 27 2024

Links

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

J. S. McCranie, A study of hyperperfect numbers, J. Int. Seqs. Vol. 3 (2000) #P00.1.3.

Mathematica

Select[Range[1500], PrimeQ[43^# - 42] &] (* Vincenzo Librandi, Sep 27 2012 *)

Prog

(PARI) for(n=2, 1500, if(isprime(43^n-42), print1(n, ", ")))

Crossrefs

Sequence in context: A355233 A377682 A145387 * A013022 A012908 A306842

Adjacent sequences: A034920 A034921 A034922 * A034924 A034925 A034926

Keyword

nonn,more

Author

Jud McCranie

Extensions

a(6) from Rick L. Shepherd, Jun 21 2002

a(7)-a(8) from Michael S. Branicky, Aug 15 2021

a(9)-a(10) from Michael S. Branicky, Mar 28 2023

Status

approved