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A291343 Numbers k such that k!4 + 2^3 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662). 1
3, 5, 7, 9, 11, 13, 19, 23, 25, 33, 39, 41, 63, 67, 71, 85, 87, 91, 133, 171, 243, 291, 1239, 1543, 1879, 2169, 2421, 3149, 3323, 3377, 3501, 3529, 5433, 5599, 7299, 11227, 11275, 13939, 27147, 32435, 86455, 92105 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 11, 13, 29, 53, 239, 593, 65843, 1514213, 5221133, ...

a(43) > 10^5.

Terms > 33 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..42.

Henri & Renaud Lifchitz, PRP Records. Search for n!4+8.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

13!4 + 2^3 = 13*9*5*1 + 8 = 593 is prime, so 13 is in the sequence.

MATHEMATICA

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

Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 4] + 2^3] &]

CROSSREFS

Cf. A007662, A037082, A084438, A123910, A242994.

Sequence in context: A309361 A133854 A239008 * A030155 A143448 A226484

Adjacent sequences:  A291340 A291341 A291342 * A291344 A291345 A291346

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 22 2017

EXTENSIONS

a(41)-a(42) from Robert Price, Sep 25 2019

STATUS

approved

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Last modified November 21 22:40 EST 2019. Contains 329383 sequences. (Running on oeis4.)