A245442 Numbers n such that (50^n - 1)/49 is prime.

3, 5, 127, 139, 347, 661, 2203, 6521, 210319

Offset

1,1

Comments

a(9) > 10^5.

All terms are prime.

Links

Table of n, a(n) for n=1..9.

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

Henri Lifchitz, Mersenne and Fermat primes field

Maple

A245442:=n->`if`(isprime((50^n - 1)/49), n, NULL); seq(A245442(n), n=1..100000); # Wesley Ivan Hurt, Apr 12 2014

Mathematica

Select[Prime[Range[100000]], PrimeQ[(50^# - 1)/49] &]

Prog

(PARI) is(n)=ispseudoprime((50^n-1)/49) \\ Charles R Greathouse IV, Jun 13 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, A242797, A243279, A245237.

Sequence in context: A070743 A340823 A364545 * A215239 A161749 A240589

Adjacent sequences: A245439 A245440 A245441 * A245443 A245444 A245445

Keyword

hard,more,nonn

Author

Robert Price, Jul 22 2014

Extensions

a(9)=210319 corresponds to a probable prime discovered by Paul Bourdelais, Aug 04 2020

Status

approved