A204662 Numbers n such that n!8-1 is prime.

3, 4, 6, 8, 10, 12, 14, 16, 18, 22, 28, 30, 42, 48, 58, 68, 80, 86, 92, 108, 110, 112, 130, 198, 220, 230, 322, 432, 460, 478, 686, 706, 714, 842, 950, 1010, 1090, 1314, 1904, 2264, 2804, 3164, 3324, 4740, 4824, 4918, 5086, 5442, 6994, 7898, 8236, 8684, 10088, 13990, 15320, 17570, 18218, 21564, 22198, 22684, 24314, 24780, 25790, 38726

Offset

1,1

Comments

n!8 = A114800(n).

No other terms < 50000. - Robert Price, Aug 15 2012

Links

Table of n, a(n) for n=1..64.

Ken Davis, Status of Search for Multifactorial Primes.

Ken Davis, Results for n!8-1.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 8] - 1] & ] (* Robert Price, Apr 19 2019 *)

Prog

(PARI) for(n=0, 9999, isprime(prod(i=0, (n-2)\8, n-8*i)-1)& print1(n", "))

Crossrefs

Cf. A204657, A204658, A204659, A204660, A204661, A204663, A204664, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981.

Sequence in context: A051755 A092535 A215476 * A135667 A156624 A341340

Adjacent sequences: A204659 A204660 A204661 * A204663 A204664 A204665

Keyword

nonn,hard

Author

M. F. Hasler, Jan 17 2012

Extensions

a(39)-a(64) from Robert Price, Aug 15 2012

Status

approved