On Wednesday, April 16, 2014 8:58:34 AM UTC-4, Alberto Verga wrote:
>
> OK, but why we need to use "limit" to compute a convergent sum...?
> For instance
>     sum(1/n^2,n,2,oo)
> gives pi^2/6-1
>
> but 
>     limit(sum(1/n^2,n,2,x), x=oo)
> do not give a result...
>
>>
>>
This is interesting.  In Sage's Maxima:

(%i1) load(simplify_sum);


(%i9) simplify_sum(sum(1/x^2,x,2,inf));
                                      2
                                   %pi
(%o9)                              ---- - 1
                                    6
(%i10) sum(log(1-1/x^2),x,2,inf);
                               inf
                               ====
                               \             1
(%o10)                          >    log(1 - --)
                               /              2
                               ====          x
                               x = 2
(%i11) simplify_sum(sum(log(1-1/x^2),x,2,inf));
                                     inf + 2
(%o11)                         log(-----------)
                                   2 (inf + 1)

Which I agree is not a great answer.  Using simpsum does the same thing. 
 I'm not sure if this is expected behavior in Maxima, though?

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