  We study the effects of Landau level mixing in the limit of weak electron
interaction. We use a numerical method to obtain the two- and three-body
corrections to quantum Hall pseudopotentials, which are exact to lowest order
in the Landau level mixing parameter. Our results are in general agreement with
certain analytic results (some derived here, some derived by other authors) in
the thermodynamic limit. We find that the convergence to this thermodynamic
limit can be slow. This suggests that errors could occur if one tries to use
pseudopotentials derived in a thermodynamic limit for numerical work on finite
systems.
