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Primes of the form k!2-4, where k!2 is the double factorial number (A006852).
1

%I #6 Dec 16 2020 15:21:03

%S 11,101,941,10391,135131,2027021,654729071,7905853580621,

%T 221643095476699771871,

%U 79777941814291672401518892224505807820921910393015244140621,6462013286957625464523030270184970433494674741834234775390621

%N Primes of the form k!2-4, where k!2 is the double factorial number (A006852).

%H Robert Price, <a href="/A289850/b289850.txt">Table of n, a(n) for n = 1..13</a>

%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n2-4&amp;action=Search">PRP Records.Search for n!2-4.</a>

%H Joe McLean, <a href="http://web.archive.org/web/20091027034731/http://uk.geocities.com/nassarawa%40btinternet.com/probprim2.htm">Interesting Sources of Probable Primes</a>

%H OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>

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

%t Select[Table[MultiFactorial[i, 2] - 4, {i, 4, 100}], PrimeQ[#]&]

%t Select[Range[4,100]!!-4,PrimeQ] (* _Harvey P. Dale_, Dec 16 2020 *)

%Y Cf. A123910.

%K nonn

%O 1,1

%A _Robert Price_, Jul 13 2017