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A291349
Numbers k such that k!4 + 2^8 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662).
1
1, 7, 11, 31, 57, 73, 97, 105, 209, 245, 403, 545, 917, 953, 1177, 1239, 1283, 1627, 2465, 3701, 4479, 4637, 6349, 7983, 11155, 13595, 15547, 17031, 17609, 24087, 24707, 39773, 40407, 63329
OFFSET
1,2
COMMENTS
Corresponding primes are: 257, 277, 487, 1267389841, ...
a(35) > 10^5.
Terms > 31 correspond to probable primes.
EXAMPLE
11!4 + 2^8 = 11*7*3*1 + 256 = 487 is prime, so 11 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 4] + 2^8] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 22 2017
EXTENSIONS
a(34) from Robert Price, Sep 25 2019
STATUS
approved