Two Other Interpretations of the Entringer Numbers |
| |
Authors: | Christiane Poupard |
| |
Institution: | Université Pierre et Marie Curie, (PARIS VI), LSTA, URA CNRS 1321, France |
| |
Abstract: | The Entringer's integers were introduced to enumerate the down-up (or up-down) permutations according to the first term. In a previous paper these integers are shown to enumerate André's trees according to two parameters. In this paper we prove that they enumerate the direct alternative permutations according to the absolute value of the first two terms and also according to a specified term. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|