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URL: https://oeis.org/A291347

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A291347
Numbers k such that k!4 + 2^6 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662).
1
3, 9, 15, 17, 19, 29, 31, 45, 55, 63, 73, 101, 135, 173, 217, 271, 439, 535, 729, 787, 933, 1473, 1651, 6617, 7805, 12461, 13253, 18627, 20243, 55271
OFFSET
1,1
COMMENTS
Corresponding primes are: 67, 109, 3529, 10009, 65899, 151412689, 1267389649, ...
a(31) > 10^5.
Terms > 31 correspond to probable primes.
EXAMPLE
15!4 + 2^6 = 15*11*7*3*1 + 64 = 3529 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] + 2^6] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 22 2017
EXTENSIONS
a(30) from Robert Price, Sep 25 2019
STATUS
approved