Enumeration of Graded (3 + 1)-Avoiding Posets
Joel Brewster Lewis, Yan X Zhang
Abstract
The notion of (3+1)-avoidance appears in many
places in enumerative combinatorics, but the natural goal of
enumerating all (3+1)-avoiding posets remains
open. In this paper, we enumerate graded (3+1)-avoiding posets. Our proof consists of a
number of structural theorems followed by some generating function
magic.
Full Text: PostScript PDF