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A289819 Primes of the form k!3-81, where k!3 is the triple factorial number (A007661). 1

%I #14 Nov 08 2023 00:37:20

%S 199,3559,12239,209359,4188719,2504902319,72642169519,528271743919,

%T 2324549427119,13106744139423334399919,2295148179742698933452799919,

%U 254451773522587035734629406212095999919,281238294844900882734503454910185471999919

%N Primes of the form k!3-81, where k!3 is the triple factorial number (A007661).

%H Harvey P. Dale, <a href="/A289819/b289819.txt">Table of n, a(n) for n = 1..32</a> (* first 19 terms from Robert Price *)

%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n3-81&amp;action=Search">PRP Records.Search for n!3-81.</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] - 81, {i, 9, 100}], PrimeQ[#]&]

%t Select[Table[Times@@Range[n,1,-3],{n,8,150}]-81,PrimeQ] (* _Harvey P. Dale_, Nov 14 2022 *)

%Y Cf. A247464.

%K nonn

%O 1,1

%A _Robert Price_, Jul 12 2017

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)