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 A204664 Numbers n such that n!8-2 is prime. 8
 4, 5, 7, 9, 11, 15, 17, 25, 27, 33, 47, 59, 63, 77, 87, 89, 93, 95, 107, 119, 127, 133, 139, 193, 201, 217, 269, 291, 369, 373, 435, 445, 669, 803, 831, 859, 907, 1271, 1705, 1743, 1849, 3087, 3189, 3497, 4221, 4475, 5119, 6013, 8023, 9237, 12755, 16501, 16747, 17021, 17309, 20671, 21539, 28377, 33625, 35645, 36831, 54663, 56223, 65299, 66159, 68121, 69339, 70579, 73511, 77745, 94601 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n!8 = A114800(n). See also links in A156165. For odd k, n!k +- 2 is even for all n > k and thus cannot be prime. a(62) > 50000. - Robert Price, Aug 27 2012 The first 10 associated primes: 2, 3, 5, 7, 31, 103, 151, 3823, 16927, 126223. - Robert Price, Mar 10 2017 a(72) > 10^5. - Robert Price, Apr 24 2017 LINKS C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75 Ken Davis, Status of Search for Multifactorial Primes. MATHEMATICA MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]]; Select[Range[4, 50000], PrimeQ[MultiFactorial[#, 8] - 2] &] (* Robert Price, Mar 10 2017 *) PROG (PARI) for(n=0, 9999, isprime(prod(i=0, (n-2)\8, n-8*i)-2)& print1(n", ")) CROSSREFS Cf. A204657, A204658, A204659, A204660, A204661, A204662, A204663, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981. Sequence in context: A339690 A267087 A050560 * A283554 A035243 A035255 Adjacent sequences:  A204661 A204662 A204663 * A204665 A204666 A204667 KEYWORD nonn,hard AUTHOR M. F. Hasler, Jan 17 2012 EXTENSIONS a(46)-a(61) from Robert Price, Aug 27 2012 a(62)-a(71) from Robert Price, Apr 24 2017 STATUS approved

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Last modified July 26 17:37 EDT 2021. Contains 346294 sequences. (Running on oeis4.)