Abstract:We give an explicit formula for the Higgs and Coulomb branch Hilbert series for the class of 3d N = 4 superconformal gauge theories T σ ρ (G) corresponding to a set of D3 branes ending on NS5 and D5-branes, with or without O3 planes. Here G is a classical group, σ is a partition of G and ρ a partition of the dual group G ∨ . In deriving such a formula we make use of the recently discovered formula for the Hilbert series of the quantum Coulomb branch of N = 4 superconformal theories. The result can be expressed in terms of a generalization of a class of symmetric functions, the Hall-Littlewood polynomials, and can be interpreted in mathematical language in terms of localization. We mainly consider the case G = SU(N ) but some interesting results are also given for orthogonal and symplectic groups.