A204940 Numbers n such that (23^n - 1)/22 is prime.

5, 3181, 61441, 91943, 121949, 221411

Offset

1,1

Comments

No other terms < 100000.

Links

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

H. Lifchitz, Mersenne and Fermat primes field

Mathematica

Select[Prime[Range[100]], PrimeQ[(23^#-1)/22]&]

Prog

(PARI) is(n)=ispseudoprime((23^n-1)/22) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A028491, A004061, A004062, A004063, A004023, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A128000, A098438, A128002, A128003, A128004, A128005.

Sequence in context: A347607 A013782 A137841 * A172954 A079173 A073826

Adjacent sequences: A204937 A204938 A204939 * A204941 A204942 A204943

Keyword

hard,nonn,more

Author

Robert Price, Jan 20 2012

Extensions

a(5)=121949 corresponds to a probable prime discovered by Paul Bourdelais, Oct 19 2017

a(6)=221411 corresponds to a probable prime discovered by Paul Bourdelais, Aug 04 2020

Status

approved