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URL: https://oeis.org/A291345

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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
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.
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] &]
Select[Range[82000], PrimeQ[Times@@Range[#, 1, -4]+32]&] (* Harvey P. Dale, Apr 11 2022 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 22 2017
EXTENSIONS
a(47)-a(49) from Robert Price, Sep 25 2019
STATUS
approved