A290116 Primes of the form k! / 2 - 1.

2, 11, 59, 359, 181439, 4111419327088961408862781439999999, 16726263306581903554085031026720375832575999999999

Offset

1,1

Links

Robert Price, Table of n, a(n) for n = 1..7

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Formula

a = (A082671(n)!-2)/2.

Example

6! / 2 - 1 = 359, which is prime, so 359 is in the sequence.
7! / 2 - 1 = 2519 = 11 * 229, so 2519 is not in the sequence.

Mathematica

Select[Table[k! / 2 - 1, {k, 2, 100}], PrimeQ[#]&]

Crossrefs

Cf. A082671, A139172.

Sequence in context: A280674 A139172 A228868 * A251180 A286194 A164034

Adjacent sequences: A290113 A290114 A290115 * A290117 A290118 A290119

Keyword

nonn

Author

Robert Price, Jul 19 2017

Status

approved