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A156165 Numbers k such that k![7]+1 is prime (n![7] = A114799(n) = septuple factorial). 11
0, 1, 2, 4, 6, 9, 10, 12, 13, 24, 25, 26, 29, 31, 35, 36, 47, 49, 57, 58, 64, 71, 73, 75, 78, 80, 97, 123, 125, 129, 131, 135, 147, 150, 159, 183, 201, 250, 251, 255, 298, 336, 337, 458, 467, 556, 570, 657, 743, 801, 908, 925, 1003, 1209, 1473, 1524, 1716, 1881, 1926 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(103) > 50000. - Robert Price, Sep 03 2012

LINKS

Robert Price, Table of n, a(n) for n = 1..102

C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75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

mf[n_, k_] := Product[n - i k, {i, 0, Quotient[n - 2, k]}];

Reap[For[k = 0, k <= 2000, k++, If[PrimeQ[mf[k, 7] + 1], Sow[k]]]][[2, 1]] (* Jean-Fran├žois Alcover, Feb 26 2019 *)

PROG

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

for( n=0, 9999, ispseudoprime(mf(n)+1) & print1(n", "))

CROSSREFS

Cf. A156167, A085150, A085148, A085146, A037083, A080778, A002981.

Sequence in context: A162202 A210380 A228359 * A024968 A047411 A288623

Adjacent sequences:  A156162 A156163 A156164 * A156166 A156167 A156168

KEYWORD

nonn

AUTHOR

M. F. Hasler, Feb 10 2009

STATUS

approved

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Last modified February 26 05:51 EST 2020. Contains 332277 sequences. (Running on oeis4.)