The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 4 02:40 EST 2021. Contains 349469 sequences. (Running on oeis4.)