A156167 - OEIS

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A156167

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

10

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

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

LINKS

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

C. Caldwell, H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75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.

MATHEMATICA

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 *)

PROG

(PARI) mf(n, k=7)=prod(i=0, (n-2)\k, n-i*k)

for( n=1, 9999, ispseudoprime(mf(n)-1) & print1(n", "))

CROSSREFS

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

Sequence in context: A325209 A121543 A080702 * A376560 A090864 A118300

Adjacent sequences: A156164 A156165 A156166 * A156168 A156169 A156170

KEYWORD

nonn

AUTHOR

M. F. Hasler, Feb 10 2009

EXTENSIONS

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

STATUS

approved