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A247467 Numbers n such that n!3 + 3^6 is prime. 0

%I

%S 4,5,7,8,10,11,14,17,35,41,50,59,89,136,164,205,224,283,763,1034,1253,

%T 1630,1820,3199,3800,5080,6124,17306,17398,20768,34033,43607

%N Numbers n such that n!3 + 3^6 is prime.

%C Large terms correspond to probable primes.

%C a(33) > 50000.

%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!3+729&amp;action=Search">PRP Records. Search for n!3+729</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>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Multifactorial.html">Multifactorial</a>

%e 11!3+729 = 11*8*5*2+729 = 1609 is prime, so 11 is in the sequence.

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

%t lst={};Do[If[PrimeQ[MultiFactorial[n, 3] + 729], AppendTo[lst, n]], {n, 100}];lst

%Y Cf. A007661, A037082, A084438, A243078.

%K nonn,more

%O 1,1

%A _Robert Price_, Sep 17 2014

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Last modified August 23 11:24 EDT 2019. Contains 326222 sequences. (Running on oeis4.)