We compute the O(1) contribution to holographic c-a for IIB supergravity on
AdS_5 x S^5/Z_n and on AdS_5 x T^{1,1}/Z_n. In both cases, we find agreement
with the dual field theory results, thus providing 1/N^2 checks of AdS/CFT with
reduced supersymmetry. Since the holographic computation involves a sum over
shortened multiplets in the KK tower, we provide some details on the S^5 and
T^{1,1} spectra in a form that is convenient when considering their Z_n
orbifolds. The computation for the even Z_n orbifolds of S^5 includes a sum
over the multiplets in the twisted sector that is essential for obtaining
agreement with the dual field theory.Comment: 23 pages, 2 figures. v2: minor corrections and references adde