  In this paper we show discrepancy bounds for index-transformed uniformly
distributed sequences. From a general result we deduce very tight lower and
upper bounds on the discrepancy of index-transformed van der Corput-, Halton-,
and $(t,s)$-sequences indexed by the sum-of-digits function. We also analyze
the discrepancy of sequences indexed by other functions, such as, e.g.,
$\lfloor n^{\alpha}\rfloor$ with $0 < \alpha < 1$.
