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 A034865 a(n) = n!*(n-4)/2. 3
 0, 60, 720, 7560, 80640, 907200, 10886400, 139708800, 1916006400, 28021593600, 435891456000, 7192209024000, 125536739328000, 2311968282624000, 44816615940096000, 912338253066240000, 19463216065413120000, 434273008459530240000, 10116006549998469120000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 4..200 J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478. FORMULA a(n) = 60 * A062199(n-5). E.g.f.: x^5/(2*(1 - x)^2). - Ilya Gutkovskiy, May 23 2017 MATHEMATICA Table[n!*(n-4)/2, {n, 4, 30}] (* Harvey P. Dale, Apr 23 2012 *) PROG (MAGMA) [Factorial(n)*(n-4)/2: n in [4..22]]; // Vincenzo Librandi, May 25 2017 (PARI) x='x+O('x^30); concat([0], Vec(serlaplace(x^5/(2*(1-x)^2)))) \\ G. C. Greubel, Feb 16 2018 CROSSREFS Sequence in context: A269189 A136008 A000555 * A138409 A024016 A112042 Adjacent sequences:  A034862 A034863 A034864 * A034866 A034867 A034868 KEYWORD nonn AUTHOR STATUS approved

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Last modified April 21 13:14 EDT 2021. Contains 343153 sequences. (Running on oeis4.)