  In this expository paper we collect some simple facts about analogues of
Pascals triangle where the entries count subsets of the integers with an even
or odd sum and show that they are related to Rogers-Szego polynomials. In
particular we consider an interesting triangle due to Losanitsch from this
point of view. We also sketch some extensions of these results to sets whose
sums have fixed residues modulo a prime $p$.
