  In a recent paper the authors studied the denominators of polynomials that
represent power sums by Bernoulli's formula. Here we extend our results to
power sums of arithmetic progressions. In particular, we obtain a simple
explicit criterion for integrality of the coefficients of these polynomials. As
applications, we obtain new results on the sequence of denominators of the
Bernoulli polynomials. A consequence is that certain quotients of successive
denominators are infinitely often integers, which we characterize.
