We extend earlier work of the same author to enumerate alternating
permutations avoiding the permutation pattern 2143. We use a generating tree
approach to construct a recursive bijection between the set A_{2n}(2143) of
alternating permutations of length 2n avoiding 2143 and standard Young tableaux
of shape (n, n, n) and between the set A_{2n + 1}(2143) of alternating
permutations of length 2n + 1 avoiding 2143 and shifted standard Young tableaux
of shape (n + 2, n + 1, n). We also give a number of conjectures and open
questions on pattern avoidance in alternating permutations and generalizations
thereof.Comment: 21 pages. To be presented at FPSAC 2010. Comments welcome
