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Re: Bug in Sum?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg119925] Re: Bug in Sum?
*From*: Bob Hanlon <hanlonr at cox.net>
*Date*: Thu, 30 Jun 2011 06:29:34 -0400 (EDT)
*Reply-to*: hanlonr at cox.net
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?
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