A034860 a(n) = n!*(2*n-5)/2.

3, 36, 300, 2520, 22680, 221760, 2358720, 27216000, 339292800, 4550515200, 65383718400, 1002550348800, 16345929600000, 282457663488000, 5157467707392000, 99236792438784000, 2007144156745728000, 42575785143091200000, 945182430176624640000, 21918014191663349760000

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

Index entries for sequences related to factorial numbers

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

N. J. A. Sloane

Status

approved