In a 1988 paper [9], Stanley introduced a class of partially ordered sets, called differential posets, defined independently by S. Fomin [1] who called them Y-graphs. The prototypical example of a differential poset is Young's lattice, Y, the lattice of integer partitions ordered by inclusion of Ferrers diagrams. Another important example is given by the Fibonacci r-differential poset, Z(r), de...
