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 A320502 a(n) = Sum_{k=0..n} (k!)^2 * abs(Stirling1(n,k)). 1
 1, 1, 5, 50, 842, 21644, 792676, 39297600, 2536525008, 206794669104, 20785423425264, 2525457805492896, 364910211591903072, 61847041340997089280, 12151693924459271926272, 2739901558132307387349504, 702704348810821821056454144, 203409730893592265642619623424 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS FORMULA a(n) ~ exp(1/2) * (n!)^2. MATHEMATICA Table[Sum[Abs[StirlingS1[n, k]]*k!^2, {k, 0, n}], {n, 0, 20}] PROG (PARI) a(n) = sum(k=0, n, k!^2*abs(stirling(n, k, 1))); \\ Michel Marcus, Oct 14 2018 (MAGMA) [(&+[Abs(StirlingFirst(n, k))*(Factorial(k))^2: k in [0..n]]): n in [0..20]]; // G. C. Greubel, Oct 14 2018 CROSSREFS Cf. A000670, A007840, A064618. Sequence in context: A052562 A113132 A088992 * A116906 A051893 A247951 Adjacent sequences:  A320499 A320500 A320501 * A320503 A320504 A320505 KEYWORD nonn AUTHOR Vaclav Kotesovec, Oct 13 2018 STATUS approved

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Last modified April 24 19:49 EDT 2019. Contains 322446 sequences. (Running on oeis4.)