  M. Saito recently proved that the jumping numbers of a hyperplane arrangement
depend only on the combinatorics of the arrangement. However, a formula in
terms of the combinatorial data was still missing. In this note, we give a
formula and a different proof of the fact that the jumping numbers of a
hyperplane arrangement depend only on the combinatorics. We also give a
combinatorial formula for part of the Hodge spectrum and for the inner jumping
multiplicities.
