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Re: Trouble with double factorial and an infinite product

  • To: mathgroup at smc.vnet.net
  • Subject: [mg84390] Re: [mg84334] Trouble with double factorial and an infinite product
  • From: Devendra Kapadia <dkapadia at wolfram.com>
  • Date: Fri, 21 Dec 2007 03:18:48 -0500 (EST)
  • References: <200712190918.EAA13893@smc.vnet.net>

On Wed, 19 Dec 2007, giovanni resta wrote:

> A collegue of mine says that evaluating this
>
> Product[1+1/n!!,{n,Infinity}]
>
> quickly kills the kernel in Mathematica 6.
> (but the same with {n,2,Infinity} does not)
>
> (The symbol n!! denotes the "double factorial" not
> the repeated application of factorial, n!!=n(n-2)(n-4)... (1 or 2).)
>
> In previous versions it seems to me that it simply
> returns it unevaluated.
>
> I'm just curious to know if it is a problem in his installation
> or a little bug.
> giovanni
>
Hello Giovanni,

The expected behavior for the above infinite product involving a double 
factorial would be for it to return unevaluated for both lower limits
of 'n'(n=1 and n=2).

The crash in the first case occurs during an attempt to transform the
first argument to an expression that does not involve the double 
factorial.

Thank you for reporting the problem. We are sorry for the inconvenience
caused by it.

Sincerely,

Devendra Kapadia,
Wolfram Research, Inc.


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