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A204659
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Numbers n such that n!9-1 is prime.
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9
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3, 4, 6, 8, 15, 20, 23, 27, 30, 44, 51, 62, 80, 90, 95, 114, 129, 138, 150, 152, 156, 182, 201, 216, 293, 332, 342, 393, 411, 414, 419, 525, 668, 743, 800, 972, 1034, 1266, 1785, 1869, 2777, 3561, 3780, 4106, 4328, 4428, 4556, 4574, 4629, 5001, 5397, 6315
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OFFSET
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1,1
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COMMENTS
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a(1)-a(73) are proved prime by the deterministic test of pfgw. - Robert Price, Jun 14 2012
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LINKS
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MATHEMATICA
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MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[1000], PrimeQ[MultiFactorial[#, 9] - 1] & ] (* Robert Price, Apr 19 2019 *)
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PROG
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(PARI) for(n=0, 9999, isprime(prod(i=0, (n-2)\9, n-9*i)-1)& print1(n", "))
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CROSSREFS
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Cf. A204657, A204658, A204660, A204661, A204662, A204663, A204664, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981.
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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Extended b-file adding a(74)-a(81) using data from Ken Davis link by Robert Price, Apr 19 2019
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STATUS
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approved
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