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 A178488 Numbers k such that 8*k! + 1 is prime. 9
 2, 4, 9, 10, 11, 12, 15, 25, 31, 46, 53, 78, 318, 615, 955, 1646, 2669, 2672, 3515 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(20) > 3810. - Jinyuan Wang, Feb 05 2020 LINKS MATHEMATICA fQ[n_] := PrimeQ[8 n! + 1]; k = 0; lst = {}; While[k < 1501, If[ fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst PROG (PARI) for(k=1, 999, ispseudoprime(8*k!+1) & print1(k, ", ")) (PFGW) ABC2 8*\$a!+1 a: from 1 to 1000 // Jinyuan Wang, Feb 05 2020 CROSSREFS Cf. A002981, A051915, A076679, A076680, A076681, A076682, A076683, A180626, A126896. Sequence in context: A275658 A267414 A072583 * A226821 A047465 A002258 Adjacent sequences:  A178485 A178486 A178487 * A178489 A178490 A178491 KEYWORD nonn,hard,more AUTHOR Robert G. Wilson v, Sep 13 2010 and M. F. Hasler, Sep 16 2010 EXTENSIONS a(16)-a(19) from Jinyuan Wang, Feb 05 2020 STATUS approved

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Last modified May 31 12:48 EDT 2020. Contains 334748 sequences. (Running on oeis4.)