A328454 Numbers k such that k![4] - 4 is prime, where k![4] = A007662(k) = quadruple factorial.

7, 9, 11, 15, 17, 19, 39, 45, 57, 59, 63, 69, 81, 85, 127, 141, 149, 153, 163, 165, 201, 235, 259, 377, 457, 649, 815, 897, 1057, 1433, 1453, 1519, 1759, 3047, 3561, 4151, 7025, 11917, 11971, 15295, 18919, 19449, 20765, 70385, 71293

Offset

1,1

Comments

a(46) > 10^5.

The first 6 primes associated with this sequence are: 17, 41, 227, 3461, 9941, 65831.

Links

Table of n, a(n) for n=1..45.

C. K. Caldwell, The Prime Glossary, multifactorial prime

C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75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.

Joe McLean, Interesting Sources of Probable Primes

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[1000], (x = MultiFactorial[#, 4] - 4; x > 0 && PrimeQ[x]) &]

Crossrefs

Cf. A007662, A283553.

Sequence in context: A024828 A139058 A242103 * A254937 A222947 A107226

Adjacent sequences: A328451 A328452 A328453 * A328455 A328456 A328457

Keyword

nonn

Author

Robert Price, Nov 06 2019

Status

approved