OFFSET
1,1
COMMENTS
Corresponding primes are: 7, 31, 631, 14071, 116471, 24663654391, 1282510028791, ...
a(30) > 10^5.
Terms > 46 correspond to probable primes.
LINKS
Henri & Renaud Lifchitz, PRP Records. Search for n!6-9.
Joe McLean, Interesting Sources of Probable Primes
OpenPFGW Project, Primality Tester
EXAMPLE
16!6 - 9 = 16*10*4 - 8 = 631 is prime, so 16 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 9] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jul 09 2017
EXTENSIONS
a(27)-a(29) from Robert Price, Aug 03 2018
STATUS
approved