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A291345 Numbers k such that k!4 + 2^5 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662). 1
5, 7, 11, 13, 19, 21, 25, 27, 35, 37, 51, 55, 65, 71, 105, 107, 129, 223, 229, 273, 307, 337, 345, 479, 509, 517, 519, 921, 963, 993, 1309, 1697, 1855, 1871, 2451, 2573, 2755, 3059, 3271, 4005, 4823, 17079, 20209, 20559, 37845, 38343, 68383, 79617, 81539 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 37, 53, 263, 617, 65867, 208877, 5221157, 40883567, ...

a(50) > 10^5.

Terms > 37 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..49.

Henri & Renaud Lifchitz, PRP Records. Search for n!4+32.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

13!4 + 2^5 = 13*9*5*1 + 32 = 617 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] + 2^5] &]

CROSSREFS

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

Sequence in context: A246463 A314297 A108409 * A298867 A039681 A216746

Adjacent sequences:  A291342 A291343 A291344 * A291346 A291347 A291348

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 22 2017

EXTENSIONS

a(47)-a(49) from Robert Price, Sep 25 2019

STATUS

approved

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Last modified October 28 11:38 EDT 2021. Contains 348329 sequences. (Running on oeis4.)