A240765 Numbers n such that (43^n - 1)/42 is prime.

5, 13, 6277, 26777, 27299, 40031, 44773, 194119

Offset

1,1

Comments

a(8) > 10^5. - Robert Price, Apr 12 2014

Links

Table of n, a(n) for n=1..8.

H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.

H. Lifchitz, Mersenne and Fermat primes field

Maple

A240765:=n->`if`(isprime((43^n - 1)/42), n, NULL); seq(A240765(n), n=1..100000); # Wesley Ivan Hurt, Apr 12 2014

Mathematica

Select[Prime[Range[100000]], PrimeQ[(43^#-1)/42]&]

Prog

(PARI) is(n)=ispseudoprime((43^n-1)/42) \\ Charles R Greathouse IV, Feb 20 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.

Sequence in context: A201260 A012173 A009143 * A127317 A049506 A069524

Adjacent sequences: A240762 A240763 A240764 * A240766 A240767 A240768

Keyword

hard,more,nonn

Author

Robert Price, Apr 12 2014

Extensions

a(8) from Paul Bourdelais, Aug 04 2020

Status

approved