[Maxima] levin_u_transform

[Michel Van den Bergh]

> I have one remaining problem. Whereas bflevin_u_sum(1/n^2,n,1) converges
> very quickly
> bflevin_u_sum(1/n^(201/100),n,1) does not converge at all. It would be
> nice if somebody could explain this to me.

I now undersand why that happens. If we sum a rational function then
the result of levin(s,k,n,beta,omega) is a rational number and hence
bfloat can compute it very accurately. Otherwise one must be much more
careful than I have been to estimate rounding errors. So for the moment
bflevin_u_sum works only reliably for rational functions. It should be
compared to sumninf which was posted earlier (which I can't run yet).

Regards,
Michel