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URL: https://oeis.org/A291348

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A291348
Numbers k such that k!4 + 2^7 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662).
1
3, 7, 9, 11, 15, 19, 29, 37, 91, 123, 151, 197, 415, 763, 1817, 2981, 3977, 4199, 11667, 12865, 16873, 19449, 27213, 31581, 64877, 65401
OFFSET
1,1
COMMENTS
Corresponding primes are: 131, 149, 173, 359, 3593, 65963, 151412753, ...
a(27) > 10^5.
Terms > 37 correspond to probable primes.
EXAMPLE
15!4 + 2^7 = 15*11*7*3*1 + 128 = 3593 is prime, so 15 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 4] + 2^7] &]
Select[Range[3000], PrimeQ[Times@@Range[#, 1, -4]+128]&] (* Harvey P. Dale, Feb 26 2023 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 22 2017
EXTENSIONS
a(25)-a(26) from Robert Price, Sep 25 2019
STATUS
approved