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The study of patterns in permutations in a very active area of current research. Klazar defined and studied an analogous notion of pattern for set partitions. We continue this work, finding exact formulas for the number of set partitions…

Combinatorics · Mathematics 2007-05-23 Bruce E. Sagan

We present a matrix-theoretic approach for studying and enumerating finite posets through their incidence representations, referred to as poset matrices. Naturally labelled posets are encoded as Boolean lower triangular matrices, allowing a…

Combinatorics · Mathematics 2026-02-05 Gi-Sang Cheon , Hong Joon Choi , Gukwon Kwon , Hojoon Lee , Yaling Wang

Indexed languages are a classical notion in formal language theory, which has attracted attention in recent decades due to its role in higher-order model checking: They are precisely the languages accepted by order-2 pushdown automata. The…

Formal Languages and Automata Theory · Computer Science 2026-05-28 Richard Mandel , Corto Mascle , Georg Zetzsche

Apr\`es avoir pos\'e les d\'efinitions n\'ecessaires \`a la compr\'ehension du sujet, nous discuterons de statistique d'inversion diagonale dans les $r$-Schr\"oder, de chemins de stationnement dans les $r$-Schr\"oder \`a pente enti\`ere et…

Combinatorics · Mathematics 2016-09-27 Nancy Wallace

The underlying structure of natural language is hierarchical; words combine into phrases, which in turn form clauses. An awareness of this hierarchical structure can aid machine learning models in performing many linguistic tasks. However,…

Machine Learning · Computer Science 2020-04-01 Ashok Thillaisundaram

We study positional statistics for four families of pattern-avoiding permutations counted by the large Schr\"oder numbers. Specifically, we focus on the pairs of patterns {2413,3142} (separable permutations), {1324,1423}, {1423,2413}, and…

Combinatorics · Mathematics 2026-03-27 Juan B. Gil , Oscar A. Lopez , Michael D. Weiner

We study a certain poset on the free monoid on a countable alphabet. This poset is determined by the fact that its total extensions are precisely the standard term orders. We also investigate the poset classifying degree-compatible standard…

Combinatorics · Mathematics 2007-05-23 Jan Snellman

Why do some languages like Czech permit free word order, while others like English do not? We address this question by pretraining transformer language models on a spectrum of synthetic word-order variants of natural languages. We observe…

Computation and Language · Computer Science 2026-03-23 Jonas Mayer Martins , Jaap Jumelet , Viola Priesemann , Lisa Beinborn

We introduce a partial order structure on the set of interval orders of a given size, and prove that such a structure is in fact a lattice. We also provide a way to compute meet and join inside this lattice. Finally, we show that, if we…

Combinatorics · Mathematics 2012-03-28 Filippo Disanto , Luca Ferrari , Simone Rinaldi

A matching of the set $[2n]=\{ 1,2,\ldots ,2n\}$ is a partition of $[2n]$ into blocks with two elements, i.e. a graph on $[2n]$ such that every vertex has degree one. Given two matchings $\sigma$ and $\tau$ , we say that $\sigma$ is a…

Combinatorics · Mathematics 2020-09-03 Matteo Cervetti , Luca Ferrari

A word $w=w_1w_2\cdots w_n$ is alternating if either $w_1<w_2>w_3<w_4>\cdots$ (when the word is up-down) or $w_1>w_2<w_3>w_4<\cdots$ (when the word is down-up). In this paper, we initiate the study of (pattern-avoiding) alternating words.…

Combinatorics · Mathematics 2015-05-18 Emma L. L. Gao , Sergey Kitaev , Philip B. Zhang

Let $\mathcal{L}_n$ denote the set of all paths from $[0,0]$ to $[n, n]$ which consist of either unit north steps $N$ or unit east steps $E$ or, equivalently, the set of all words $L \in \{E,N\}^*$ with $n$ $E$'s and $n$ $N$'s. Given $L \in…

Combinatorics · Mathematics 2017-08-25 Ran Pan , Jeffrey B. Remmel

We introduce the notion of unavoidable (complete) sets of word patterns, which is a refinement for that of words, and study certain numerical characteristics for unavoidable sets of patterns. In some cases we employ the graph of pattern…

Combinatorics · Mathematics 2007-05-23 Alexander Burstein , Sergey Kitaev

Patience Sorting is a combinatorial algorithm that can be viewed as an iterated, non-recursive form of the Schensted Insertion Algorithm. In recent work the authors have shown that Patience Sorting provides an algorithmic description for…

Combinatorics · Mathematics 2007-05-23 Alexander Burstein , Isaiah Lankham

Pattern avoidance classes of permutations that cannot be expressed as unions of proper subclasses can be described as the set of subpermutations of a single bijection. In the case that this bijection is a permutation of the natural numbers…

Combinatorics · Mathematics 2007-05-23 M. D. Atkinson , M. M. Murphy , N. Ruskuc

Probabilistic puzzles can be confusing, partly because they are formulated in natural languages - full of unclarities and ambiguities - and partly because there is no widely accepted and intuitive formal language to express them. We propose…

Logic in Computer Science · Computer Science 2025-04-11 Elena Di Lavore , Bart Jacobs , Mario Román

Do state-of-the-art natural language understanding models care about word order - one of the most important characteristics of a sequence? Not always! We found 75% to 90% of the correct predictions of BERT-based classifiers, trained on many…

Computation and Language · Computer Science 2021-07-27 Thang M. Pham , Trung Bui , Long Mai , Anh Nguyen

Special scattered subwords, in which the gaps are of length from a given set, are defined. The scattered subword complexity, which is the number of such scattered subwords, is computed for rainbow words.

Discrete Mathematics · Computer Science 2011-04-25 Zoltán Kása

Natural language processing area is still under research. But now a day it is on platform for worldwide researchers. Natural language processing includes analyzing the language based on its structure and then tagging of each word…

Computation and Language · Computer Science 2013-07-23 Miral Patel , Prem Balani

Words are fundamental linguistic units that connect thoughts and things through meaning. However, words do not appear independently in a text sequence. The existence of syntactic rules induces correlations among neighboring words. Using an…

Computation and Language · Computer Science 2023-03-15 David Sanchez , Luciano Zunino , Juan De Gregorio , Raul Toral , Claudio Mirasso