A034865 a(n) = n!*(n-4)/2.

0, 60, 720, 7560, 80640, 907200, 10886400, 139708800, 1916006400, 28021593600, 435891456000, 7192209024000, 125536739328000, 2311968282624000, 44816615940096000, 912338253066240000, 19463216065413120000, 434273008459530240000, 10116006549998469120000

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.

Index entries for sequences related to factorial numbers

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 A348583

Adjacent sequences: A034862 A034863 A034864 * A034866 A034867 A034868

Keyword

nonn

Author

N. J. A. Sloane

Status

approved