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A289686 Numbers k such that k!6 - 8 is prime, where k!6 is the sextuple factorial number (A085158). 1
9, 11, 13, 15, 19, 27, 35, 39, 45, 51, 83, 99, 105, 111, 121, 123, 127, 133, 175, 177, 213, 263, 277, 285, 339, 347, 543, 681, 743, 1069, 1965, 2379, 2613, 2629, 2911, 3767, 3879, 4789, 5493, 5819, 11559, 14555, 17831, 19705, 24867, 37535, 85089 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 19, 47, 83, 397, 1721, 229627, 21827567, ...

a(48) > 10^5.

Terms > 99 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..47.

Henri & Renaud Lifchitz, PRP Records. Search for n!6-8.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

19!6 - 8 = 19*13*7 - 8 = 1721 is prime, so 19 is in the sequence.

MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];

Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 8] &]

CROSSREFS

Cf. A007661, A037082, A084438, A123910, A242994.

Sequence in context: A008558 A335912 A123760 * A251394 A155877 A214865

Adjacent sequences:  A289683 A289684 A289685 * A289687 A289688 A289689

KEYWORD

nonn

AUTHOR

Robert Price, Jul 09 2017

EXTENSIONS

a(47) from Robert Price, Aug 03 2018

STATUS

approved

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Last modified May 20 21:39 EDT 2022. Contains 353876 sequences. (Running on oeis4.)