cp's OEIS Frontend

A289755 Primes of the form k!9-1, where k!9 is the nonuple factorial number (A114806).

%I A289755 #20 Jul 31 2025 08:41:49
%S A289755 2,3,5,7,89,439,1609,4373,22679,5445439,152681759,17893715839,
%T A289755 101636305971199,12652843234348799,266565181393279999,
%U A289755 4929089879840974847999,16401565050020468398079999,2263415976902824638935039999,1692607074564424130419507199999
%N A289755 Primes of the form k!9-1, where k!9 is the nonuple factorial number (A114806).
%H A289755 Harvey P. Dale, <a href="/A289755/b289755.txt">Table of n, a(n) for n = 1..41</a> (Terms 1 through 33 from Robert Price)
%H A289755 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=k%219-1&amp;action=Search">PRP Records. Search for k!9-1</a>.
%H A289755 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 A289755 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%t A289755 MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
%t A289755 Select[Table[MultiFactorial[i, 9] - 1, {i, 2, 100}], PrimeQ[#]&]
%t A289755 Select[Table[Times@@Range[n,1,-9]-1,{n,200}],PrimeQ] (* _Harvey P. Dale_, Sep 12 2019 *)
%Y A289755 Cf. A204659.
%K A289755 nonn
%O A289755 1,1
%A A289755 _Robert Price_, Jul 11 2017