OFFSET
1,3
COMMENTS
n!9 = A114806(n).
a(107) > 50000. - Robert Price, Jun 18 2012
a(1)-a(106) verified prime by deterministic test of PFGW. - Robert Price, Jun 18 2012
LINKS
Robert Price, Table of n, a(n) for n = 1..106
Ken Davis, Status of Search for Multifactorial Primes.
Ken Davis, Results for n!9+1.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 9] + 1] & ] (* Robert Price, Apr 19 2019 *)
Select[Range[0, 800], PrimeQ[Times@@Range[#, 1, -9]+1]&] (* Harvey P. Dale, Aug 19 2021 *)
PROG
(PARI) for(n=0, 9999, isprime(prod(i=0, (n-2)\9, n-9*i)+1)& print1(n", "))
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
M. F. Hasler, Jan 17 2012
STATUS
approved