# [seqfan] Re: Mathematica's or my err?

zak seidov zakseidov at yahoo.com
Sat Apr 24 15:37:44 CEST 2010

```Thanks, David!
Alex Povolotsky also pointed (privately) me to WolframAlpha!

Anyone with  Mathematica 7.1 or
Maple 8?!

Zak

--- On Sat, 4/24/10, David W. Cantrell <DWCantrell at sigmaxi.net> wrote:

> From: David W. Cantrell <DWCantrell at sigmaxi.net>
> Subject: [seqfan] Re: Mathematica's or my err?
> To: "Sequence Fans" <seqfan at seqfan.eu>
> Date: Saturday, April 24, 2010, 9:23 AM
> It's an error present in Mathematica
> versions 5.1 and 6.0, at least.
>
> so I
> checked with Wolfram Alpha. Asked to compute
>
> Sum[(1/i)*Binomial[2n-i-1,i-1],{i,1,n}]
>
> it returns
>
> (-1 + Hypergeometric2F1[1/2 - n, -n, 1 - 2 n, -4])/(2 n)
>
> That seems to be a correct answer, and so I would guess
> that the
> current version of Mathematica does not have the error you
> noticed.
>
> David
>
>
> ----- Original Message -----
> From: "zak seidov" <zakseidov at yahoo.com>
> To: "seqfaneu" <seqfan at seqfan.eu>
> Sent: Saturday, April 24, 2010 12:05
> Subject: [seqfan] Mathematica's or my err?
>
>
> > Dear seqfans with Mathematica
> > (or other tools?!),
> > anyone may wish to check this strange result:
> >
> > FullSimplify[Sum[(1/i)*Binomial[2n-i-1,i-1],{i,1,n}]]
> =
> > (2^(-1 - 2*n)*(-4^n + (1 + Sqrt[5])^(2*n)))/n
> >
> > I use M 5.1.
> > Thanks, Zak
> >
> >
> >
> >
> >
> > _______________________________________________
> >
> > Seqfan Mailing list - http://list.seqfan.eu/
>
>
>
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>
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>

```