论文信息 - A proof of Julian West's conjecture that the number of two-stacksortable permutations of length n is 2(3n)!/((n + 1)!(2n + 1)!)

A proof of Julian West's conjecture that the number of two-stacksortable permutations of length n is 2(3n)!/((n + 1)!(2n + 1)!)

Abstract The Polya-Schutzenberger-Tutte methodology of weight enumeration, combined with about 10 hours of CPU time (of Maple running on Drexel University's Sun network) established Julian West's conjecture that 2-stack-sortable permutations are enumerated by sequence # 651 in the Sloane listing.

Doron Zeilberger | D. Zeilberger

[1] Julian West,et al. Sorting Twice Through a Stack , 1993, Theor. Comput. Sci..

[2] Marcel Paul Schützenberger,et al. On Context-Free Languages and Push-Down Automata , 1963, Inf. Control..

[3] G. Pólya. On Picture-Writing , 1956 .

[4] W. T. Tutte,et al. A Contribution to the Theory of Chromatic Polynomials , 1954, Canadian Journal of Mathematics.