A294722 Numbers k such that (44^k - 1)/43 is prime.

5, 31, 167, 100511

Offset

1,1

Comments

The number corresponding to a(4) is a probable prime.

These are the indices of base-44 repunit primes, i.e., numbers k such that A002275(k) interpreted as a base-44 number and converted to decimal is prime. - Felix Fröhlich, Nov 08 2017

Links

Table of n, a(n) for n=1..4.

P. Bourdelais, A generalized repunit conjecture

Mathematica

ParallelMap[ If[ PrimeQ[(44^# - 1)/43], #, Nothing] &, Prime@Range @ 10000] (* Robert G. Wilson v, Nov 25 2017 *)

Prog

(PFGW) ABC2 (44^$a-1)/43 // -f{2*$a}
a: primes from 2 to 1000000
(PARI) is(n) = ispseudoprime((44^n-1)/43) \\ Felix Fröhlich, Nov 08 2017

Crossrefs

Cf. A028491, A004061, A004062, A004063, A004023, A005808, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A098438, A128002, A128003, A128004, A128005, A240765.

Sequence in context: A092496 A045904 A034353 * A237622 A239334 A180635

Adjacent sequences: A294719 A294720 A294721 * A294723 A294724 A294725

Keyword

nonn,more

Author

Paul Bourdelais, Nov 07 2017

Status

approved