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

5, 3181, 61441, 91943, 121949, 221411

Offset: 1

Author

Robert Price, Jan 20 2012

Keywords

• hard
• nonn
• more

Comments

No other terms < 100000.

Links

• H. Lifchitz, Mersenne and Fermat primes field

Crossrefs

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

Programs

Mathematica

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

PARI

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

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