Re: Bug in Sum?

*To*: mathgroup at smc.vnet.net*Subject*: [mg119971] Re: Bug in Sum?*From*: Dana DeLouis <dana01 at me.com>*Date*: Sat, 2 Jul 2011 05:02:21 -0400 (EDT)

Hi. I've noticed over time that Mathematica doesn't work well with specific values in the power function, just as you noticed. It's been this way for a while. I find that using a variable for the power usually works well. Hence... Sum[1/((n*(1 + n))*(1 - x)^p), {n, 1, m}] m/((1 - x)^p*(1 + m)) Then... put your power of 4 back in: % /. p -> 4 m/((1 + m)*(1 - x)^4) Just note that the capital letter M is a reserve word in the Combinatorica Package. = = = = = = = = = = HTH : >) Dana DeLouis $Version 8.0 for Mac OS X x86 (64-bit) (November 6, 2010) On Jun 29, 5:42 pm, Dario <dario.benede... 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?