Catalan words are particular growth-restricted words counted by the eponymous integer sequence. In this article we consider Catalan words avoiding a pair of patterns of length 3, pursuing the recent initiating work of the first and last authors and of S. Kirgizov where (among other things) the enumeration of Catalan words avoiding a patterns of length 3 is completed. More precisely, we explore systematically the structural properties of the sets of words under consideration and give enumerating results by means of recursive decomposition, constructive bijections or bivariate generating functions with respect to the length and descent number. Some of the obtained enumerating sequences are known, and thus the corresponding results establish new combinatorial interpretations for them.
翻译:加泰罗尼亚词是按地名整数顺序计算的特定限制增长的字数。 在本条中,我们考虑加泰罗尼亚词,避免第三长线的一对图案,继续第一作者和最后作者以及S.Kirgizov最近启动的工作,在那里(除其他外)完成了加泰罗尼亚词的列举,避免第三长线的图案。更准确地说,我们系统地探讨所考虑的各组字的结构性特性,并通过递转分解、建设性分解或产生关于长度和下行数的双轨函数来计算结果。一些获得的列数序列是已知的,因此相应的结果为它们提供了新的组合解释。