  We study the N=2 four-dimensional superconformal index in various interesting
limits, such that only states annihilated by more than one supercharge
contribute. Extrapolating from the SU(2) generalized quivers, which have a
Lagrangian description, we conjecture explicit formulae for all A-type quivers
of class S, which in general do not have one. We test our proposals against
several expected dualities. The index can always be interpreted as a correlator
in a two-dimensional topological theory, which we identify in each limit as a
certain deformation of two-dimensional Yang-Mills theory. The structure
constants of the topological algebra are diagonal in the basis of Macdonald
polynomials of the holonomies.
