A051592 - OEIS

A051592

Numbers k such that k!!!!!! - 1 is prime.

3, 4, 6, 12, 14, 54, 74, 102, 114, 302, 318, 366, 614, 1178, 1188, 3110, 7284, 21432, 21906, 25848, 29882, 38618, 41990, 84510, 86022

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OFFSET

1,1

COMMENTS

k!!!!!! = k*(k-6)*(k-12)*(k-18)*...

The search for multifactorial primes started by Ray Ballinger is now continued by a team of volunteers on the website of Ken Davis (see link).

LINKS

MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];

Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 6] - 1] & ] (* Robert Price, Apr 19 2019 *)

CROSSREFS

Cf. A085158 (sextuple factorials), A085150.

KEYWORD

hard,nonn

AUTHOR

EXTENSIONS

Edited and extended by Hugo Pfoertner, Jun 23 2003

Corrected and extended by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

STATUS

approved