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 A123438 Numbers n such that the denominator of n!/!n (= A000142(n)/A000166(n)) is prime. 0
 4, 5, 6, 7, 10, 11, 15, 16, 34, 44, 63, 66, 168, 427, 575, 928, 1094, 1218, 1363, 1713 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS That is, numbers n such that A053557(n) is prime. - Michel Marcus, Aug 28 2013 LINKS MATHEMATICA a[n_] := Sum[(-1)^k/k!, {k, 0, n}]; Select[Range[100], PrimeQ[Numerator[a[#]]] &] (* G. C. Greubel, Oct 31 2017 *) PROG (PARI) isok(n) = isprime(numerator(sum(k=0, n, (-1)^k/k!))); \\ Michel Marcus, Aug 28 2013 CROSSREFS Cf. A000142, A000166, A053557. Sequence in context: A172999 A354489 A284371 * A039024 A065028 A107756 Adjacent sequences: A123435 A123436 A123437 * A123439 A123440 A123441 KEYWORD nonn,more AUTHOR Ed Pegg Jr, Jul 11 2008 EXTENSIONS a(16)-a(20) from G. C. Greubel, Nov 01 2017 STATUS approved

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Last modified January 26 16:14 EST 2023. Contains 359833 sequences. (Running on oeis4.)