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 A034860 a(n) = n!*(2*n-5)/2. 1
 3, 36, 300, 2520, 22680, 221760, 2358720, 27216000, 339292800, 4550515200, 65383718400, 1002550348800, 16345929600000, 282457663488000, 5157467707392000, 99236792438784000, 2007144156745728000, 42575785143091200000, 945182430176624640000, 21918014191663349760000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 3..200 J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478 FORMULA (-2*n+7)*a(n) + n*(2*n-5)*a(n-1) = 0. - R. J. Mathar, Apr 03 2017 E.g.f.: x^3*(1 + x)/(2*(1 - x)^2). - Ilya Gutkovskiy, May 23 2017 MATHEMATICA Table[n!*(2*n-5)/2, {n, 3, 20}] (* Harvey P. Dale, Oct 10 2012 *) PROG (MAGMA) [Factorial(n)*(2*n-5)/2: n in [3..22]]; // Vincenzo Librandi, May 25 2017 (PARI) for(n=3, 30, print1(n!*(2*n-5)/2, ", ")) \\ G. C. Greubel, Feb 16 2018 CROSSREFS Sequence in context: A056299 A212616 A073980 * A220831 A003691 A038146 Adjacent sequences:  A034857 A034858 A034859 * A034861 A034862 A034863 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified March 24 10:11 EDT 2018. Contains 301183 sequences. (Running on oeis4.)