wrong sum with conditional function



I'm on Maxima 5.19.2 and I get the same result.
With setcheck set to true I see:

(%i10) sum(d(k),k,0,a);
k SET TO g16510
(%o10) a+1

what does g16510 stand for? I remember there was a discussion about such 
values some time ago but I don't find it.

Moreover, doesn't Maxima knows about Gauss' formula?

(%i11) sum(x,x,1,n);
(%o11) 'sum(x,x,1,n)

Maxima returns a noun form, instead of n*(n+1)/2

Stefano



In data sabato 19 dicembre 2009 18:14:15, Alexandros Droseltis ha scritto:
: > Hello!
> 
> [using Maxima 5.19.0.]
> 
> Please have a look at this:
> 
> (%i1) d(k) := if k=0 then 0 else 1;
> (%o1)                   d(k) := if k = 0 then 0 else 1
> (%i2) assume(a>0);
> (%o2)                               [a > 0]
> (%i3) sum(d(k), k, 0, a);
> (%o3)                                a + 1
> (%i4)
> 
> How comes this +1 in the result?
> 
> Best Regards
> 
> Alexandros
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