newbie question concerning recursion

hi,

On Fri, 2006-11-24 at 12:02 +0100, Hugo Coolens wrote:
>
> Thanks for the quick reply, I changed the syntax as you suggested but 
> entering zth[2]; gives:
> 
>   zth(1) s + 1
> 
> ------------------
> 
> (zth(1) + 1) s + 1
> 
> and not:
> 
> (1+2*s)/(1+3*s+s^2)

try

(%i12) radcan( zth[2] );

                                   2 s + 1
(%o12)                           ------------
                                  2
                                 s  + 3 s + 1


Miquel