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Re: Symbolic summation

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  • Subject: [mg101595] Re: Symbolic summation
  • From: Peter Breitfeld <phbrf at>
  • Date: Fri, 10 Jul 2009 23:22:23 -0400 (EDT)
  • References: <h3761n$f3i$>

Luca wrote:

> Hello all, I have a problem, I've to compute a symbolic summation,
> which takes a very long time if I have to do it by hand. I have to
> write the terms of the Volterra series, related to the associated
> linear equation of a system.
> The problem is that I'm not really confident with mathematica, I've
> tried to use symbolic calculations with sums, but I think that in my
> case is not so easy.
> The problem is that I want a solution of this form:
> x1+x2+x3+x4+x5...
> Where the 1, 2, 3 and 4 and 5 are the summation subscripts...
> My summation is not infinite, I have to stop it.
> If I write something like this:
> n = 3;
> Sum[kl, {l, 2, n}]
> I obtain 2kl, instead I want to obtain k2+k3.
> Is it possible with mathematica?


kl is one symbol for Mathematica, so your input of Sum[kl,{l,2,n}] will
be evaluated to kl+kl.
You have to make l a variable, like this:



Sum[Subscript[a, l], {l, 2, 10}]

Peter Breitfeld, Bad Saulgau, Germany --

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