  We conjecture a closed-form expression for the Schur limit of the
superconformal index of two infinite series of Argyres-Douglas (AD)
superconformal field theories (SCFTs): the (A_1,A_{2n-3}) and the (A_1,D_{2n})
theories. While these SCFTs can be realized at special points on the Coulomb
branch of certain N=2 gauge theories, their superconformal R symmetries are
emergent, and hence their indices cannot be evaluated by localization. Instead,
we construct the (A_1, A_{2n-3}) and (A_1, D_{2n}) indices by using a relation
to two-dimensional q-deformed Yang-Mills theory and data from the class S
construction. Our results generalize the indices derived from the torus
partition functions of the two-dimensional chiral algebras associated with the
(A_1, A_3) and (A_1, D_4) SCFTs. As checks of our conjectures, we study the
consistency of our results with an S-duality recently discussed by us in
collaboration with Giacomelli and Papageorgakis, we reproduce known Higgs
branch relations, we check consistency with a series of renormalization group
flows, and we verify that the small S^1 limits of our indices reproduce
expected Cardy-like behavior. We will discuss the S^1 reduction of our indices
in a separate paper.
