  We investigate binary voting systems with two types of voters and a hierarchy
among the members in each type, so that members in one class have more
influence or importance than members in the other class. The purpose of this
paper is to count, up to isomorphism, the number of these voting systems for an
arbitrary number of voters. We obtain a closed formula for the number of these
systems, this formula follows a Fibonacci sequence with a smooth polynomial
variation on the number of voters.
