I need help in Maxima (a "simple" problem [how is the syntax for the formula])

Dear Sirs, Madam,

I was proning that people should use OpenSource programs like Maxima, or at
least try. Many people on that forum are math people or engineers. I said,
well I can't afford Maxima, etc. And that Maxima is not bad for students and
people should try it Well now Maxima's honour is at stake.

Here is the problem I need a quick solution for to show Holger:


I was looking at Maxima (installed maxima-5.9.3 and wxMaxima-0.6.5) and
would like to solve something like the following (ie. I thought it would be
a good idea to start with something simple from my thesis):

a, b, n natural numbers > 0
a+b <= x
how many solutions f(x) exists
with { a+b | a * b }, ie a*b = (a+b) * n

as a starter. Has anyone an idea how to start - browsing through the
documentation of maxima did't give me an idea.

Regards,
Holger