A289817 - OEIS

A289817

Primes of the form k!3-9, where k!3 is the triple factorial number (A007661).

%I #4 Jul 13 2017 21:26:45

%S 19,71,271,3631,58231,209431,4188791,96342391,17041023991,72642169591,

%T 2324549427191,1143053268797439991,52580450364682239991,

%U 262134882788466687991,694657439389436723199991,38900816605808456499199991,2295148179742698933452799991

%N Primes of the form k!3-9, where k!3 is the triple factorial number (A007661).

%H Robert Price, <a href="/A289817/b289817.txt">Table of n, a(n) for n = 1..24</a>

%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n3-9&action=Search">PRP Records.Search for n!3-9.</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, 3] - 9, {i, 5, 100}], PrimeQ[#]&]

%Y Cf. A243078.

%K nonn

%O 1,1

%A _Robert Price_, Jul 12 2017