cp's OEIS Frontend

A204661 Numbers n such that n!8+1 is prime (for n!8 see A114800).

%I A204661 #25 Apr 12 2022 12:55:48
%S A204661 0,1,2,4,6,28,30,46,60,72,86,90,112,154,162,206,280,354,400,512,606,
%T A204661 614,678,790,938,1054,1092,1148,1582,1788,2088,2206,2598,2912,3672,
%U A204661 4642,6272,6428,7084,7604,8580,9464,12762,18386,24910,30448,31696,40288,41682,45730
%N A204661 Numbers n such that n!8+1 is prime (for n!8 see A114800).
%C A204661 n!8 = A114800(n).
%C A204661 No other terms < 50000. - _Robert Price_, Jul 29 2012
%H A204661 Ken Davis, <a href="http://mfprimes.free-dc.org">Status of Search for Multifactorial Primes</a>.
%H A204661 Ken Davis, <a href="http://mfprimes.free-dc.org/mfdata/f08p.html">Results for n!8+1.</a>
%t A204661 MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
%t A204661 Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 8] + 1] & ] (* _Robert Price_, Apr 19 2019 *)
%t A204661 Select[Range[0,46000],PrimeQ[Times@@Range[#,1,-8]+1]&] (* _Harvey P. Dale_, Apr 12 2022 *)
%o A204661 (PARI) for(n=0,9999,isprime(prod(i=0,(n-2)\8,n-8*i)+1)& print1(n","))
%Y A204661 Cf. A204657, A204658, A204659, A204660, A204662, A204663, A204664, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981.
%K A204661 nonn,hard
%O A204661 1,3
%A A204661 _M. F. Hasler_, Jan 17 2012
%E A204661 a(35)-a(50) from _Robert Price_, Jul 29 2012