ratgf keyword

[Ralf Stephan]

> I would vote for a couple more keywords for periodic and monotonic
> sequences.

Yes, and I propose a ratgf keyword for sequences proven to have 
rational generating functions. Neil, I'm willing to put some work
into this, e.g., by giving you a list with members.

The problem with this and the above proposed keywords, however,
is how to constantly maintain new entries. Ideas?


ralf