We will study the Poincaré series for the multiplicities of induced modules and restriction modules in the tensor algebra T(V) in connection with the McKay-Slodowy correspondence. In particular, it is shown that the closed formulas for the Poincaré series associated with the distinguished pairs of subgroups of SU(2) give rise to the exponents of all untwisted and twisted affine Lie algebras. This is joint work with H. Zhang and D. Wang.