A289860 Primes of the form k!4 - 2, where k!4 is the quadruple factorial number (A007662).

2, 3, 19, 43, 229, 3463, 208843, 5221123, 151412623, 16713607661375623, 1027438963906784290227656915623, 7419136758370889359733910587728123, 64138437276116338514899657030909640623, 99213846986734491072350087622336908512964418837890623

Offset: 1

Author

Robert Price, Jul 13 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..23
• Henri and Renaud Lifchitz, PRP Records.Search for n!4-2.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A007662, A283554.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 4] - 2, {i, 3, 100}], PrimeQ[#]&]

Formula

a(n) = A007662(A283554(n)) - 2. - Elmo R. Oliveira, Feb 25 2025