I used two sets of benchmarks.  The first was compiled by Roy Dyckhoff for
a comparison of propositional theorem provers at the Tableaux98
conference.  These are parameterised benchmarks -- the idea, of course,
being to see for how big an n can the 'formula' be proved in a fixed time.
I note that the link of Roy's page has broken and have attached the prolog
version to this message (I think Roy may have versions in other
languages).

Secondly, I have a few formulae which I threw together in an ad hoc way.
These range from trivial to testing. They are written as prolog predicates
in my (hard to read) syntax.  I shall attach the smaller ones of these to
the next message. (I have larger ones instantiating firstorder formulae
over finite domains, but these are unwieldy).  (2, 9, 10, 12 are
unprovable, the others provable).

It rather messy, but I hope they are of some use,

Jacob