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A289687 Numbers k such that k!6 - 9 is prime, where k!6 is the sextuple factorial number (A085158). 1
8, 10, 16, 22, 26, 46, 52, 56, 70, 74, 286, 302, 308, 484, 698, 1100, 1226, 1528, 2486, 3796, 4256, 8524, 10688, 19424, 22226, 49346, 53746, 64178, 84304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 7, 31, 631, 14071, 116471, 24663654391, 1282510028791, ...

a(30) > 10^5.

Terms > 46 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..29.

Henri & Renaud Lifchitz, PRP Records. Search for n!6-9.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

16!6 - 9 = 16*10*4 - 8 = 631 is prime, so 16 is in the sequence.

MATHEMATICA

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

Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 9] &]

CROSSREFS

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

Sequence in context: A270796 A058633 A165143 * A155966 A228072 A038209

Adjacent sequences:  A289684 A289685 A289686 * A289688 A289689 A289690

KEYWORD

nonn,more

AUTHOR

Robert Price, Jul 09 2017

EXTENSIONS

a(27)-a(29) from Robert Price, Aug 03 2018

STATUS

approved

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Last modified May 27 16:48 EDT 2022. Contains 354110 sequences. (Running on oeis4.)