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A204660
Numbers n such that n!9+1 is prime.
9
0, 1, 2, 4, 6, 10, 11, 12, 13, 14, 16, 17, 18, 19, 21, 24, 25, 32, 40, 43, 48, 49, 50, 57, 60, 71, 73, 82, 83, 86, 97, 105, 114, 121, 142, 147, 159, 168, 195, 205, 210, 212, 233, 262, 288, 289, 300, 309, 316, 323, 356, 403, 447, 505, 514, 553, 735, 739, 777
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
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", "))
KEYWORD
nonn,hard
AUTHOR
M. F. Hasler, Jan 17 2012
STATUS
approved