A085147 -id:A085147 - cp's OEIS frontend

A085146 Numbers k such that k!!!! + 1 is prime.

0, 1, 2, 4, 6, 18, 38, 56, 94, 118, 148, 286, 1358, 1480, 1514, 2680, 2846, 4078, 4288, 5612, 5680, 6440, 6586, 14614, 30972, 31690, 54406

Offset: 1

Hugo Pfoertner, Jun 25 2003

The search for multifactorial primes started by Ray Ballinger is now continued by a team of volunteers on the website of Ken Davis (see link).

Ken Davis, Status of Search for Multifactorial Primes.
Ken Davis, Results for n!4+1.

Cf. A007662 (quadruple factorials), A085147.

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

A156167 Numbers n such that n![7]-1 is prime (where n![7] = A114799(n) = septuple factorial).

Original entry on oeis.org

3, 4, 6, 8, 9, 10, 11, 12, 14, 17, 20, 24, 30, 31, 32, 46, 52, 54, 59, 98, 104, 143, 145, 160, 174, 198, 199, 202, 212, 215, 254, 371, 382, 452, 674, 739, 959, 1249, 1657, 2291, 2553, 2650, 3562, 3727, 3853, 4389, 4604, 5449, 5659, 6026, 6878, 7900, 9564, 10150, 12444, 13321, 22642, 24014, 26598, 27430, 31386, 40707, 43328, 45811

Offset: 1

M. F. Hasler, Feb 10 2009

nonn

a(65) > 50000. - Robert Price, Sep 09 2012

C. Caldwell, H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75
Ken Davis, Status of Search for Multifactorial Primes.
Ken Davis, Results for n!7-1.

cf. A156165, A051592, A085149, A085147, A084438, A007749, A002982.

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 7] - 1] & ] (* Robert Price, Apr 19 2019 *)

mf(n,k=7)=prod(i=0,(n-2)\k,n-i*k)
for( n=1,9999, ispseudoprime(mf(n)-1) & print1(n","))

a(43)-a(64) from Robert Price, Sep 09 2012

cp's OEIS Frontend

A085146 Numbers k such that k!!!! + 1 is prime.

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