  Symanzik effective actions, conjectured to describe lattice artifacts, are
determined for a class of lattice regularizations of the non-linear O(N) sigma
model in two dimensions in the leading order of the 1/N-expansion. The class of
actions considered includes also ones which do not have the usual classical
limit and are not (so far) treatable in the framework of ordinary perturbation
theory. The effective actions obtained are shown to reproduce previously
computed lattice artifacts of the step scaling functions defined in finite
volume, giving further confidence in Symanzik's theory of lattice artifacts.
