A283485 Numbers k such that k![6]-2 is prime, where k![6] = A085158 (k) = sextuple factorial.

4, 5, 7, 11, 13, 23, 25, 31, 33, 37, 59, 63, 91, 157, 265, 267, 327, 539, 555, 621, 715, 921, 979, 1633, 1821, 2259, 2697, 2809, 2863, 2935, 4213, 4351, 5937, 6885, 8743, 10761, 15159, 17685, 52075, 55147, 68677, 99655

Offset: 1

Author

Robert Price, Mar 08 2017

Keywords

• nonn

Comments

a(43) > 10^5.

The first 10 primes associated with this sequence: 2, 3, 5, 53, 89, 21503, 43223, 1339973, 7577953, 49579073.

Links

• C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75
• Ken Davis, Status of Search for Multifactorial Primes.

Crossrefs

Cf. A076185, A085158, A094144, A204657.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[2, 50000], PrimeQ[MultiFactorial[#, 6] - 2] &]
Select[Range[100000],PrimeQ[Times@@Range[#,1,-6]-2]&] (* Harvey P. Dale, Feb 23 2023 *)

Extensions

a(39)-a(42) from Robert Price, Jul 09 2017