A088984 a(n) = (n!!)^2 - n!.

2, 3, 40, 105, 1584, 5985, 107136, 530145, 11116800, 68139225, 1644364800, 12034447425, 329001523200, 2801155982625, 85619242598400, 831764543234625, 28117244819865600, 307025061241523625, 11374945402060800000

Offset

2,1

Links

Table of n, a(n) for n=2..20.

Formula

E.g.f.: x*(1 - sqrt(1 - x^2) + arcsin(x))/(1 - x^2)^(3/2). - Benedict W. J. Irwin, Oct 14 2016

Mathematica

Table[CoefficientList[Series[(x(1-Sqrt[1-x^2]+ArcSin[x]))/(1-x^2)^(3/2), {x, 0, 20}], x][[n]](n-1)!, {n, 3, 20}] (* Benedict W. J. Irwin, Oct 14 2016 *)

Crossrefs

Sequence in context: A111683 A323734 A347817 * A355843 A097170 A231797

Adjacent sequences: A088981 A088982 A088983 * A088985 A088986 A088987

Keyword

nonn

Author

Vladeta Jovovic, Oct 31 2003

Status

approved