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A247865 Numbers n such that n!3 + 3^2 is prime.

%I A247865 #9 Feb 16 2025 08:33:23
%S A247865 2,4,5,7,8,14,17,19,22,23,26,34,46,59,70,86,100,101,118,148,151,160,
%T A247865 200,281,317,343,682,842,853,871,1244,1988,2170,2389,2728,3049,3661,
%U A247865 4678,9169,12767,16072,19808,20710,33142,33442
%N A247865 Numbers n such that n!3 + 3^2 is prime.
%C A247865 Large terms correspond to probable primes.
%C A247865 a(46) > 50000.
%H A247865 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!3+9&amp;action=Search">PRP Records. Search for n!3+9</a>
%H A247865 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 A247865 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%H A247865 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Multifactorial.html">Multifactorial.</a>
%e A247865 8!3+9 = 8*5*2+9= 89 is prime, so 8 is in the sequence.
%t A247865 MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
%t A247865 lst={};Do[If[PrimeQ[MultiFactorial[n, 3] + 9], AppendTo[lst, n]], {n, 100}];lst
%Y A247865 Cf. A007661, A037082, A084438, A243078.
%K A247865 nonn,more
%O A247865 1,1
%A A247865 _Robert Price_, Sep 25 2014