The Terwilliger algebra of an almost-bipartite P- and Q-polynomial association scheme

John S. Caughman, Mark S. MacLean, Paul M. Terwilliger

Let $Y$ denote a $D$-class symmetric association scheme with $D\ge 3$, and suppose $Y$ is almost-bipartite P- and Q-polynomial. Let $x$ denote a vertex of $Y$ and let $T=T(x)$ de…