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A204658
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Numbers n such that n!10-1 is prime.
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8
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3, 4, 6, 8, 12, 20, 40, 48, 60, 62, 70, 84, 88, 168, 240, 258, 372, 760, 932, 1010, 2110, 2464, 2490, 2702, 3180, 4744, 6024, 8858, 9060, 10322, 13382, 15778, 19322, 22372, 22928, 25344, 28050, 40604, 42282, 45884, 52428, 58250, 81220, 93612, 108650
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OFFSET
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1,1
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COMMENTS
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n!10 = product( n-10k, 0 <= k < n/10 ).
a(1)-a(40) are proved prime by deterministic tests of pfgw. - Robert Price, Jun 11 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[#, 10] - 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)\10, n-10*i)-1)& print1(n", "))
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CROSSREFS
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Cf. A204657, A204659, 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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a(41)-a(45) from Ken Davis link entered by Robert Price, Apr 19 2019
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STATUS
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approved
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