Re: Bug in Sum?

*To*: mathgroup at smc.vnet.net*Subject*: [mg119939] Re: Bug in Sum?*From*: Phil J Taylor <xptaylor at gmail.com>*Date*: Thu, 30 Jun 2011 20:40:03 -0400 (EDT)*References*: <201106301029.GAA15424@smc.vnet.net>

Works in version 6.0 In[1]:= Sum[1/(n (1 + n)) 1/((1 - x)^4), {n, 1, M}] $Version Out[1]= M/((1 + M) (1 - x)^4) Out[2]= "6.0 for Microsoft Windows (32-bit) (June 19, 2007)" On Thu, Jun 30, 2011 at 6:29 AM, Bob Hanlon <hanlonr at cox.net> wrote: > > For a workaround, generalize the problem > > Sum[1/(n (1 + n)) 1/((1 - x)^r), {n, 1, M}] > > M/((1 - x)^r*(1 + M)) > > % /. r -> 4 > > M/((1 + M)*(1 - x)^4) > > > Bob Hanlon > > ---- Dario <dario.benedetti at aei.mpg.de> wrote: > > ============= > I am very puzzled by the fact that Mathematica does not evaluate the > following Sum (it keeps running endlessly): > > Sum[1/(n (1 + n)) 1/((1 - x)^4) , {n, 1, M}] > > where x and M are some undefined variables, > > but it does evaluate > > Sum[1/(n (1 + n)) 1/((1 - x)^2) , {n, 1, M}] > > where I have only changed the power of (1-x), which should not matter as it > must factor out! > > Any help on this please? > > > >

**References**:**Re: Bug in Sum?***From:*Bob Hanlon <hanlonr@cox.net>