  Partition function of beta-gamma systems on the orbifolds C^2/Z_N and C^3/Z_M
x Z_N are obtained as the invariant part of that on the respective affine
spaces, by lifting the geometric action of the orbifold group to the fields.
Interpreting the sum over roots of unity as an elementary contour integration,
the partition function evaluates to an infinite series counting invariant
monomials composed of basic operators of the theory at each mass level.
