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

Author

N. J. A. Sloane

Keywords

• nonn

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

Programs

Magma

[Factorial(n)*(n-4)/2: n in [4..22]]; // Vincenzo Librandi, May 25 2017

Mathematica

Table[n!*(n-4)/2,{n,4,30}] (* Harvey P. Dale, Apr 23 2012 *)

PARI

x='x+O('x^30); concat([0], Vec(serlaplace(x^5/(2*(1-x)^2)))) \\ G. C. Greubel, Feb 16 2018

Formula

a(n) = 60 * A062199(n-5).

E.g.f.: x^5/(2*(1 - x)^2). - Ilya Gutkovskiy, May 23 2017