A289689 Numbers k such that k!6 - 16 is prime, where k!6 is the sextuple factorial number (A085158).

9, 15, 17, 65, 129, 135, 209, 225, 327, 357, 423, 1061, 1143, 3629, 4937, 6713, 33123, 79185, 88323, 89933

Offset

1,1

Comments

Corresponding primes are: 11, 389, 919, 8549258359016359, 17694587964658118355578965371540271859, ...

a(21) > 10^5.

Terms > 17 correspond to probable primes.

Links

Table of n, a(n) for n=1..20.

Henri & Renaud Lifchitz, PRP Records. Search for n!6-16.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

17!6 - 16 = 17*11*5 - 16 = 919 is prime, so 17 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[6, 50000], PrimeQ[MultiFactorial[#, 6] - 16] &]

Crossrefs

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

Sequence in context: A061838 A037002 A071149 * A316752 A358725 A358576

Adjacent sequences: A289686 A289687 A289688 * A289690 A289691 A289692

Keyword

nonn,more

Author

Robert Price, Jul 09 2017

Extensions

a(18)-a(20) from Robert Price, Aug 03 2018

Status

approved