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A283554 Numbers k such that k![4] - 2 is prime, where k![4] = A007662(k) = quadruple factorial. 1

%I

%S 4,5,7,9,11,15,21,25,29,49,79,87,95,125,133,153,157,185,201,217,223,

%T 289,323,469,533,567,821,1001,1999,2523,2533,2827,2843,4821,8153,8947,

%U 12739,19353,22929,30629,31809,37785,74913,97411

%N Numbers k such that k![4] - 2 is prime, where k![4] = A007662(k) = quadruple factorial.

%C a(45) > 10^5.

%C The first 9 primes associated with this sequence: 2, 3, 19, 43, 229, 3463, 208843, 5221123, 151412623.

%H C. Caldwell and H. Dubner (Eds): <a href="http://primes.utm.edu/lists/top_ten/">The top ten prime numbers: from the unpublished collections of R. Ondrejka</a> (May 2001), Table 21 F, p. 75

%H Ken Davis, <a href="http://mfprimes.free-dc.org">Status of Search for Multifactorial Primes</a>.

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

%t Select[Range[2, 50000], PrimeQ[MultiFactorial[#, 4] - 2] &]

%Y Cf. A076185, A085158, A094144, A204657.

%K nonn

%O 1,1

%A _Robert Price_, Mar 10 2017

%E a(43)-a(44) from _Robert Price_, Jul 24 2017

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Last modified July 29 17:41 EDT 2021. Contains 346346 sequences. (Running on oeis4.)