A279646 Numbers k such that k!6 - 3 is prime, where k!6 is the sextuple factorial number (A085158).

5, 6, 8, 10, 68, 82, 92, 98, 118, 286, 796, 878, 1360, 1502, 1516, 1568, 1646, 3628, 3716, 4048, 7982, 12776, 18070, 20594, 29902, 39632, 52988, 53864, 55610, 67448, 85402, 89762

Offset

1,1

Comments

Corresponding primes are: 2, 3, 13, 37, 73569236156415997, ...

a(33) > 10^5.

Terms > 10 correspond to probable primes.

Links

Table of n, a(n) for n=1..32.

Henri & Renaud Lifchitz, PRP Records. Search for n!6-3.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

10!6 - 3 = 10*4 - 3 = 37 is prime, so 10 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[4, 50000], PrimeQ[MultiFactorial[#, 6] - 3] &]

Crossrefs

Cf. A007661, A037082, A084438, A123910, A242994.

Sequence in context: A385720 A330916 A113935 * A291640 A088766 A332549

Adjacent sequences: A279643 A279644 A279645 * A279647 A279648 A279649

Keyword

nonn,more

Author

Robert Price, Jul 07 2017

Extensions

a(27)-a(32) from Robert Price, Aug 03 2018

Status

approved