login
A289697
Numbers k such that k!6 - 24 is prime, where k!6 is the sextuple factorial number (A085158).
1
9, 11, 13, 17, 23, 25, 29, 31, 37, 43, 53, 65, 71, 77, 79, 115, 119, 151, 173, 559, 793, 1571, 1715, 1807, 1861, 2047, 2215, 3491, 4751, 6631, 9089, 9139, 9253, 25811, 29491, 29495, 54335, 54991, 66535, 72365
OFFSET
1,1
COMMENTS
Corresponding primes are: 3, 31, 67, 911, 21481, 43201, 623621, 1339951, ...
a(41) > 10^5.
Terms > 43 correspond to probable primes.
EXAMPLE
13!6 - 4 = 13*7*1 - 24 = 67 is prime, so 13 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[9, 50000], PrimeQ[MultiFactorial[#, 6] - 24] &]
Select[Range[8, 5000], PrimeQ[Times@@Range[#, 1, -6]-24]&] (* Harvey P. Dale, Dec 01 2018 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jul 09 2017
EXTENSIONS
a(37)-a(40) from Robert Price, Aug 03 2018
STATUS
approved