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

 

Logo

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!)
A163085 Product of first n swinging factorials (A056040). 9
1, 1, 2, 12, 72, 2160, 43200, 6048000, 423360000, 266716800000, 67212633600000, 186313420339200000, 172153600393420800000, 2067909047925770649600000, 7097063852481244869427200000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

With the definition of the Hankel transform as given by Luschny (see link) which uniquely determines the original sequence (provided that all determinants are not zero) this is also 1/ the Hankel determinant of 1/(n+1) (assuming (0,0)-based matrices).

a(2*n-1) is 1/determinant of the Hilbert matrix H(n) (A005249).

a(2*n) = A067689(n). - Peter Luschny, Sep 18 2012

LINKS

Table of n, a(n) for n=0..14.

Peter Luschny, SequenceTransformations

MAPLE

a := proc(n) local i; mul(A056040(i), i=0..n) end;

MATHEMATICA

a[0] = 1; a[n_] := a[n] = a[n-1]*n!/Floor[n/2]!^2; Table[a[n], {n, 0, 14}] (* Jean-François Alcover, Jun 26 2013 *)

PROG

(Sage)

def A056040(n):

    swing = lambda n: factorial(n)/factorial(n//2)^2

    return mul(swing(i) for i in (0..n))

[A056040(i) for i in (0..14)] # Peter Luschny, Sep 18 2012

CROSSREFS

Cf. A056040, A163086, A055462, A000178.

Sequence in context: A235359 A130426 A002397 * A328946 A037515 A037718

Adjacent sequences:  A163082 A163083 A163084 * A163086 A163087 A163088

KEYWORD

nonn

AUTHOR

Peter Luschny, Jul 21 2009

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 1 15:57 EST 2021. Contains 349430 sequences. (Running on oeis4.)