  Solving numerically master equation for a recently introduced urn model, we
show that the fourth- and sixth-order cumulants remain constant along an
exactly located line of critical points. Obtained values are in very good
agreement with values predicted by Brezin and Zinn-Justin for the Ising model
above the critical dimension. At the tricritical point cumulants acquire values
which also agree with a suitably extended Brezin and Zinn-Justin approach.
