Enumeration of rhombus tilings of a hexagon which contain a fixed rhombus on its symmetry axis

Abstract

We compute the number of rhombus tilings of a hexagon with sides $N,M,N,N,M,N$, which contain a fixed rhombus on the symmetry axis. A special case solves a problem posed by Jim Propp.

21 pages, AmS-LaTeX, uses TeXDraw Extended Abstract, submitted to FPSAC'98