A289697 Numbers k such that k!6 - 24 is prime, where k!6 is the sextuple factorial number (A085158).

9, 11, 13, 17, 23, 25, 29, 31, 37, 43, 53, 65, 71, 77, 79, 115, 119, 151, 173, 559, 793, 1571, 1715, 1807, 1861, 2047, 2215, 3491, 4751, 6631, 9089, 9139, 9253, 25811, 29491, 29495, 54335, 54991, 66535, 72365

Offset

1,1

Comments

Corresponding primes are: 3, 31, 67, 911, 21481, 43201, 623621, 1339951, ...

a(41) > 10^5.

Terms > 43 correspond to probable primes.

Links

Table of n, a(n) for n=1..40.

Henri & Renaud Lifchitz, PRP Records. Search for n!6-24.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

13!6 - 4 = 13*7*1 - 24 = 67 is prime, so 13 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[9, 50000], PrimeQ[MultiFactorial[#, 6] - 24] &]
Select[Range[8, 5000], PrimeQ[Times@@Range[#, 1, -6]-24]&] (* Harvey P. Dale, Dec 01 2018 *)

Crossrefs

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

Sequence in context: A225557 A120177 A291350 * A104296 A254936 A117675

Adjacent sequences: A289694 A289695 A289696 * A289698 A289699 A289700

Keyword

nonn,more

Author

Robert Price, Jul 09 2017

Extensions

a(37)-a(40) from Robert Price, Aug 03 2018

Status

approved