[seqfan] Re: definition of double factorial
Max Alekseyev
maxale at gmail.com
Tue Oct 20 17:20:36 CEST 2009
OEIS says, for example:
%N A001147 Double factorial numbers: (2n-1)!! = 1.3.5....(2n-1).
%p A001147 A001147 := proc(n) doublefactorial(2*n-1); end: [From R. J.
Mathar (mathar(AT)strw.leidenuniv.nl), Jul 04 2009]
Maple's documentation for doublefactorial(n) reads in part:
"When n is a positive integer, this definition is equivalent to the product:
* n(n-2)...(6)(4)(2) if n is an even, positive integer
* n(n-2)...(5)(3)(1) if n is an odd, positive integer"
Where is the inconsistency?
Regards,
Max
On Tue, Oct 20, 2009 at 6:35 AM, Karol <penson at lptl.jussieu.fr> wrote:
> This is to inform you that the definition of double factorial numbers
> as given in A001147(n) and in related sequences as A001818(n) etc.
> disagrees with Maple's
> function doublefactorial(n). I do not know if this point was raised
> before.
> As this may lead to inconsistencies I intend to submit a comment on it.
>
> Karol A.Penson
>
>
>
>
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