  We conjecture closed-form expressions for the Macdonald limits of the
superconformal indices of the (A_1, A_{2n-3}) and (A_1, D_{2n}) Argyres-Douglas
(AD) theories in terms of certain simple deformations of Macdonald polynomials.
As checks of our conjectures, we demonstrate compatibility with two
S-dualities, we show symmetry enhancement for special values of n, and we argue
that our expressions encode a non-trivial set of renormalization group flows.
Moreover, we demonstrate that, for certain values of n, our conjectures imply
simple operator relations involving composites built out of the SU(2)_R
currents and flavor symmetry moment maps, and we find a consistent picture in
which these relations give rise to certain null states in the corresponding
chiral algebras. In addition, we show that the Hall-Littlewood limits of our
indices are equivalent to the corresponding Higgs branch Hilbert series. We
explain this fact by considering the S^1 reductions of our theories and showing
that the equivalence follows from an inequality on monopole quantum numbers
whose coefficients are fixed by data of the four-dimensional parent theories.
Finally, we comment on the implications of our work for more general N=2
superconformal field theories.
