A090703 Numbers k such that k*k! + 1 is prime.

1, 2, 3, 4, 5, 7, 12, 19, 23, 45, 58, 149, 151, 197, 682, 879, 1134, 1906, 6616, 10242, 12015

Offset

1,2

Links

Table of n, a(n) for n=1..21.

Formula

a(n) = A049432(n) - 1.

Example

3*3! + 1 = 19 and 19 is prime, so 3 is a member.

Mathematica

Do[If[PrimeQ[n*n! + 1], Print[n]], {n, 0, 2000}] (* Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), May 05 2006 *)

Prog

(PARI) isok(k) = ispseudoprime(k*k! + 1); \\ Altug Alkan, Mar 22 2018

Crossrefs

Cf. A049432.

Sequence in context: A240732 A060437 A133428 * A352820 A137357 A100676

Adjacent sequences: A090700 A090701 A090702 * A090704 A090705 A090706

Keyword

nonn,more

Author

mohammed bouayoun (bouyao(AT)wanadoo.fr), Jan 15 2004

Extensions

a(17) from Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), May 05 2006

a(18)-a(19) from Jason Earls, Jan 24 2008

a(20) from Seiichi Manyama (by using the data calculated by Donovan Johnson, Dec 18 2009), Mar 22 2018

a(21) from Michael S. Branicky, Jun 11 2025

Status

approved