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A204659 Numbers n such that n!9-1 is prime.

%I A204659 #31 Nov 12 2019 11:34:47
%S A204659 3,4,6,8,15,20,23,27,30,44,51,62,80,90,95,114,129,138,150,152,156,182,
%T A204659 201,216,293,332,342,393,411,414,419,525,668,743,800,972,1034,1266,
%U A204659 1785,1869,2777,3561,3780,4106,4328,4428,4556,4574,4629,5001,5397,6315
%N A204659 Numbers n such that n!9-1 is prime.
%C A204659 n!9 = A114806(n).
%C A204659 a(74) > 50000. - _Robert Price_, Jun 14 2012
%C A204659 a(1)-a(73) are proved prime by the deterministic test of pfgw. - _Robert Price_, Jun 14 2012
%H A204659 Robert Price, <a href="/A204659/b204659.txt">Table of n, a(n) for n = 1..81</a>
%H A204659 Ken Davis, <a href="http://mfprimes.free-dc.org">Status of Search for Multifactorial Primes</a>.
%H A204659 Ken Davis, <a href="http://mfprimes.free-dc.org/mfdata/f09m.html">Results for n!9-1.</a>
%t A204659 MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
%t A204659 Select[Range[1000], PrimeQ[MultiFactorial[#, 9] - 1] & ] (* _Robert Price_, Apr 19 2019 *)
%o A204659 (PARI) for(n=0,9999,isprime(prod(i=0,(n-2)\9,n-9*i)-1)& print1(n","))
%Y A204659 Cf. A204657, A204658, A204660, A204661, A204662, A204663, A204664, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981.
%K A204659 nonn,hard
%O A204659 1,1
%A A204659 _M. F. Hasler_, Jan 17 2012
%E A204659 a(47)-a(73) from _Robert Price_, Jun 14 2012
%E A204659 Extended b-file adding a(74)-a(81) using data from Ken Davis link by _Robert Price_, Apr 19 2019