multivariable taylor series
I know how to generate a multivairiable Taylor series and extract its coefficients. What I want to do is to extract all the terms where the exponents of the individual variables satisfy certain requirements.
So for instance, my function is f(x,y)=(1/(1-xy))(1/(1-xy^2))(1/(1-xy^3))(1-x*y^4))
What I want is all terms in the Taylor series such that the exponent on x is at most 10 and the exponent on y is at most 20. Ideas?