       Re: bug in Mathematica?

• To: mathgroup at smc.vnet.net
• Subject: [mg122674] Re: bug in Mathematica?
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Sat, 5 Nov 2011 04:48:11 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201111041103.GAA29326@smc.vnet.net>

```This is clearly a rather nasty bug. To see it more clearly:

f[m_, k_] := Product[Binomial[m, j], {j, 1, k}]

For numerical m and k we get the correct answer:

f[10, 2]

450

For symbolic n and m we get nonsense:

In:=
f[m, n] /. {m -> 10, n -> 2}
During evaluation of In:= Power::infy:Infinite expression 1/0^2 encountered. >>
During evaluation of In:= Infinity::indet:Indeterminate expression 0 ComplexInfinity encountered. >>
Out=
Indeterminate

In particular:

f[m, m - 1]

0

f[m, m + 1]

(I^(m*(m + 5))*m*(m*BarnesG[1 - m])^m*BarnesG[2 - m]^(-m - 1))/
BarnesG[m + 3]

which is also nonsense, since

Binomial[n, n + 1]

0

Andrzej Kozlowski

On 4 Nov 2011, at 12:03, Hansruedi Widmer wrote:

> Hi Everyone
>
>
> The code
>
> Sum[Binomial[m, j], {j, 1, m - 1}]
>
> produces the correct value -2+2^m.
>
>
> But the code
>
> Product[Binomial[m, j], {j, 1, m - 1}]
>
> creates the wrong value of zero. Does anyone have an explanation for why
> this is happening?
>
>
> Thanks and best regards
>
> Hansrued Widmer
>
>
>
>

```

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