Helmut Prodinger
S-Motzkin paths (bijective to ternary trees) and partial version of them are calculated using only elementary methods from linear algebra.
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Refined enumeration of two-rowed set-valued standard tableaux via two-coloured Motzkin paths
本文通过建立两行集值标准表与双色 Motzkin 路径的双射，结合生成函数与拉格朗日反演公式，给出了按各行条目数精细计数的显式公式。
Enumeration of interval-closed sets via Motzkin paths and quarter-plane walks
本文通过构造双射分别将两条链之积偏序集的区间闭集映射到双色Motzkin路径，将截断矩形偏序集的区间闭集映射到四分仪游走，从而求得了对应的生成函数与函数方程。
A generalized Motzkin path, called G-Motzkin path for short, of length $n$ is a lattice path from $(0, 0)$ to $(n, 0)$ in the first quadrant of the XOY-plane that consists of up steps $\mathbf{u}=(1, 1)$, down steps $\mathbf{d}=(1, -1)$, horizontal steps $\mathbf{h}=(1, 0)$ and vertical steps $\mathbf{v}=(0, -1)$. An $(a,b,c)$-G-Motzkin path is a weighted G-Motzkin path such that the $\mathbf{u}$-steps, $\mathbf{h}$-steps, $\mathbf{v}$-steps and $\mathbf{d}$-steps are weighted respectively by $1, a, b$ and $c$. In this paper, we first give bijections between the set of $\mathbf{uvu}$-avoiding …
The enumeration of standard Young tableaux (SYTs) of shape λ can be easily computed by the hook-length formula. In 1981, Amitai Regev proved that the number of SYTs having at most three rows with n entries equals the nth Motzkin number M_n. In 2006, Regev conjectured that the total number of SYTs of skew shape λ/(2, 1) over all partitions λ having at most three parts with n entries is the difference of two Motzkin numbers, M_{n-1} - M_{n-3}. Ekhad and Zeilberger proved Regev's conjecture using a computer program. In 2009, S.-P. Eu found a bijection between Motzkin paths and SYTs of skew shape …
We present a higher genus generalization of $bc$-Motzkin numbers, which are themselves a generalization of Catalan numbers, and we derive a recursive formula which can be used to calculate them. Further, we show that this leads to a topological recursion which is identical to the topological recursion that had previously been proved by Dumitrescu and Mulase for generalized Catalan numbers, and which is an example of the Eynard-Orantin topological recursion.
So called $S$-Motzkin paths are combined the concepts `catastrophes' and `air pockets. The enumeration is done by properly set up bivariate generating functions which can be extended using the kernel method.
Dyck paths where peaks are only allowed on level 1 and on even-indexed levels, were introduced by Retakh and analysed by Zeilberger, with assistance from Ekhad. We add some combinatorial comments to the enumeration, which involves Motzkin numbers, in particular, about the average height of such objects.
We classify and enumerate the idempotents in several planar diagram monoids: namely, the Motzkin, Jones (a.k.a. Temperley-Lieb) and Kauffman monoids. The classification is in terms of certain vertex- and edge-coloured graphs associated to Motzkin diagrams. The enumeration is necessarily algorithmic in nature, and is based on parameters associated to cycle components of these graphs. We compare our algorithms to existing algorithms for enumerating idempotents in arbitrary (regular *-) semigroups, and give several tables of calculated values.
This article introduces and investigates a refinement of alternating sign trapezoids by means of Catalan objects and Motzkin paths. Alternating sign trapezoids are a generalisation of alternating sign triangles, which were recently introduced by Ayyer, Behrend and Fischer. We show that the number of alternating sign trapezoids associated with a Catalan object (resp. Motzkin path) is a polynomial function in the length of the shorter base of the trapezoid. We also study the rational roots of the polynomials and formulate several conjectures and derive some partial results. Lastly, we deduce a c…
Enumeration of paths in a hexagonal circle packing
针对六边形圆堆积中的路径，本文用函数方程、核方法等推导其生成函数、渐近结果，建立与三类经典路径的双射，证明相关阵列为Riordan阵列并得到连分数展开。
Motzkin paths of bounded height with two forbidden contiguous subwords of length two
本文在禁止模式背景下研究限高Motzkin路径，通过建立二元生成函数并利用核方法展开，推导出矩阵方程与连分数以完成路径枚举。
A variation of Dyck paths allows for down-steps of arbitrary length, not just one. Credits for this invention are given to Emeric Deutsch. Surprisingly, the enumeration of them is somewhat akin to the analysis of Motzkin-paths; the last section contains a bijection.
Using a recursive approach, we show that the generating function for sets of Motzkin paths avoiding a single (not necessarily consecutive) pattern is rational over $x$ and the Catalan generating function $C(x) = \frac{1-\sqrt{1-4x^2}}{2x^2}$, where $x$ keeps track of the length of the path. Moreover, an algorithm is provided for finding the generating function in the more general case of an arbitrary set of patterns. In addition, this algorithm allows us to find a combinatorial specification for pattern-avoiding Motzkin paths, which can be used not only for enumeration, but also for exhaustive…
We enumerate the edges in the Hasse diagram of several lattices arising in the combinatorial context of lattice paths. Specifically, we will consider the case of Dyck, Grand Dyck, Motzkin, Grand Motzkin, Schröder and Grand Schröder lattices. Finally, we give a general formula for the number of edges in an arbitrary Young lattice (which can be interpreted in a natural way as a lattice of paths).
Motzkin paths consist of up-steps, down-steps, level-steps, and never go below the $x$-axis. They return to the $x$-axis at the end. The concept of skew Dyck path \cite{Deutsch-italy} is transferred to skew Motzkin paths, namely, a left step $(-1,-1)$ is additionally allowed, but the path is not allowed to intersect itself. The enumeration of these combinatorial objects was known \cite{Qing}; here, using the kernel method, we extend the results by allowing them to end at a prescribed level $j$. The approach is completely based on generating functions. Asymptotics of the total number of objects…
For any pattern $α$ of length at most two, we enumerate equivalence classes of Łukasiewicz paths of length $n\geq 0$ where two paths are equivalent whenever the occurrence positions of $α$ are identical on these paths. As a byproduct, we give a constructive bijection between Motzkin paths and some equivalence classes of Łukasiewicz paths.
Peakless Motzkin paths of bounded height
本文研究有界高度的无峰 Motzkin 路径，利用核方法与生成函数奇异性分析给出带状区域内的计数结果，并推导出平均高度渐近式 $2\cdot 5^{-1/4}\sqrt{πn}$。
The Tamari lattice, defined on Catalan objects such as binary trees and Dyck paths, is a well-studied poset in combinatorics. It is thus natural to try to extend it to other families of lattice paths. In this article, we fathom such a possibility by defining and studying an analogy of the Tamari lattice on Motzkin paths. While our generalization is not a lattice, each of its connected components is isomorphic to an interval in the classical Tamari lattice. With this structural result, we proceed to the enumeration of components and intervals in the poset of Motzkin paths we defined. We also ex…
In this paper, we introduce a new family of generalized colored Motzkin paths, where horizontal steps are colored by means of $F_{k,l}$ colors, where $F_{k,l}$ is the $l$th $k$-Fibonacci number. We study the enumeration of this family according to the length. For this, we use infinite weighted automata.
Motzkin paths with two variants of level steps on odd levels -- a kernel method approach
本文研究了在奇数层上允许两种水平步的Motzkin路径的计数问题，采用核方法建立生成函数的解析关系，并推导出满足holonomic递推关系的系数序列。
Bijective Enumeration and Sign-Imbalance for Permutation Depth and Excedances
本研究提出Biane双射的简化变体，通过带权3色Motzkin路径构造排列对合，证明了深度与超位数的奇偶计数性质，并给出按二者细化的排列及错位排列符号不平衡结果。
Kasraoui, Stanton and Zeng, and Kim, Stanton and Zeng introduced certain $q$-analogues of Laguerre and Charlier polynomials. The moments of these orthogonal polynomials have combinatorial models in terms of crossings in permutations and set partitions. The aim of this article is to prove simple formulas for the moments of the $q$-Laguerre and the $q$-Charlier polynomials, in the style of the Touchard-Riordan formula (which gives the moments of some $q$-Hermite polynomials, and also the distribution of crossings in matchings). Our method mainly consists in the enumeration of weighted Motzkin pa…
The exact enumeration of pure dimer coverings on the square lattice was obtained by Kasteleyn, Temperley and Fisher in 1961. In this paper, we consider the monomer-dimer covering problem (allowing multiple monomers) which is an outstanding unsolved problem in lattice statistics. We have developed the state matrix recursion method that allows us to compute the number of monomer--dimer coverings and to know the partition function with monomer and dimer activities. This method proceeds with a recurrence relation of so-called state matrices of large size. The enumeration problem of pure dimer cove…
In this paper we consider the enumeration of orientable and non-orientable chord diagrams. We show that this enumeration is encoded in appropriate expectation values of the $β$-deformed Gaussian and RNA matrix models. We evaluate these expectation values by means of the $β$-deformed topological recursion, and - independently - using properties of quantum curves. We show that both these methods provide efficient and systematic algorithms for counting of chord diagrams with a given genus, number of backbones and number of chords.
Enumeration on polyominoes determined by Catalan words avoiding $(\geq,\geq)$
本文研究了避免 $(\geq,\geq)$ 模式的 Catalan 字关联的 Motzkin polyomino，推导了基于长度、面积、半周长等参数的生成函数及闭式表达式，并将结果表示为三项式系数的线性组合。
Fibonacci Polyominoes: Refined Enumeration and Dyck-Path Bijections
本文研究 Fibonacci 多联骨牌的按面积和半周长枚举，通过生成函数得到含 Catalan 数的精细公式，并建立与带标签 Dyck 路径的双射，将统计量转化为峰与返回，还研究等高连续列并得到 Motzkin 数控制的精细化。
Richardson tableaux and Motzkin paths
本文从莫茨金路径视角研究理查森表，引入独立于RS算法的形状算法，构造局部双射并重新证明q计数公式，还证明了郭关于特定理查森表生成函数的猜想。
We introduce the boundary length and point spectrum, as a joint generalization of the boundary length spectrum and boundary point spectrum in arXiv:1307.0967. We establish by cut-and-join methods that the number of partial chord diagrams filtered by the boundary length and point spectrum satisfies a recursion relation, which combined with an initial condition determines these numbers uniquely. This recursion relation is equivalent to a second order, non-linear, algebraic partial differential equation for the generating function of the numbers of partial chord diagrams filtered by the boundary …
We introduce and study the new combinatorial class of Dyck paths with air pockets. We exhibit a bijection with the peakless Motzkin paths which transports several pattern statistics and give bivariate generating functions for the distribution of patterns as peaks, returns and pyramids. Then, we deduce the popularities and asymptotic expectations of these patterns and point out a link between the popularity of pyramids and a special kind of closed smooth self-overlapping curves, a subset of Fibonacci meanders. A similar study is conducted for non-decreasing Dyck paths with air pockets.
Continued fractions for permutation statistics
本文通过循环图可视化排列与彩色Motzkin路径的双射，将排列统计量转化为路径统计量，利用连分数获得新枚举公式，并证明超越数递增的循环排列由贝尔数计数。
Topological recursion for spin enumeration of hypermaps
本文针对超图自旋计数建立拓扑递归，因谱曲线为椭圆型、含退化分歧点及移动极点等特性，需调整拓扑递归与回路方程，计算涉及BKP可积性等概念。
Generating 2-Gray codes for grand Motzkin paths and grand Dyck paths with air pockets in constant amortized time
本文提出首个已知的2-Gray码用于具有气穴的大Motzkin路径和大Dyck路径，采用三阶段算法，每个字符串的常数摊销时间生成，并给出计数公式。
We consider various classes of Motzkin trees as well as lambda-terms for which we derive asymptotic enumeration results. These classes are defined through various restrictions concerning the unary nodes or abstractions, respectively: We either bound their number or the allowed levels of nesting. The enumeration is done by means of a generating function approach and singularity analysis. The generating functions are composed of nested square roots and exhibit unexpected phenomena in some of the cases. Furthermore, we present some observations obtained from generating such terms randomly and exp…
Recently Mansour and Shattuck studied $(k,a)$-paths and gave formulas that relate the total number of humps (peaks) in all $(k,a)$-paths to the number of super $(k,a)$-paths. These results generalize earlier results of Regev on Dyck paths and Motzkin paths. Their proofs are based on generating functions and they asked for bijective proofs for their results. In this paper we first give bijective proofs of Mansour and Shattuck's results, then we extend our study to $(n,m)$-Dyck paths. We give a bijection that relates the total number of peaks in all $(n,m)$-Dyck paths to certain free $(n,m)$-pat…
The Goulden-Jackson cluster method is a powerful tool for obtaining generating functions for counting words in a free monoid by occurrences of a set of subwords. We introduce a generalization of the cluster method for monoid networks, which generalize the combinatorial framework of free monoids. As a sample application of the generalized cluster method, we compute bivariate and multivariate generating functions counting Motzkin paths---both with height bounded and unbounded---by statistics corresponding to the number of occurrences of various subwords, yielding both closed-form and continued f…
Enumeration of multi-rooted plane trees
本文给出了多根平面树计数的闭式表达式、递推关系及生成函数显式形式，并附带新二项式恒等式和超几何函数猜想。
We consider the system of equations $A_k(x)=p(x)A_{k-1}(x)(q(x)+\sum_{i=0}^k A_i(x))$ for $k\geq r+1$ where $A_i(x)$, $0\leq i \leq r$, are some given functions and show how to obtain a close form for $A(x)=\sum_{k\geq 0}A_k(x)$. We apply this general result to the enumeration of certain subsets of Dyck, Motzkin, skew Dyck, and skew Motzkin paths, defined recursively according to the first return decomposition with a monotonically non-increasing condition relative to the maximal ordinate reached by an occurrence of a given pattern $π$.
Combinatorial enumeration of lattice paths by flaws with respect to a linear boundary of rational slope
本文研究了具有有理斜率线性边界缺陷的格路径枚举问题，通过证明特定子集的双射关系推导出所有情况下的闭式表达式。
In this paper we determine two asymptotic results for Jack measures on partitions, a model defined by two specializations of Jack polynomials proposed by Borodin-Olshanski in [European J. Combin. 26.6 (2005): 795-834]. Assuming these two specializations are the same, we derive limit shapes and Gaussian fluctuations for the anisotropic profiles of these random partitions in three asymptotic regimes associated to diverging, fixed, and vanishing values of the Jack parameter. To do so, we introduce a generalization of Motzkin paths we call "ribbon paths", show for general Jack measures that certai…
We give a characterisation of the idempotents of the partition monoid, and use this to enumerate the idempotents in the finite partition, Brauer and partial Brauer monoids, giving several formulae and recursions for the number of idempotents in each monoid as well as various $\mathscr R$-, $\mathscr L$- and $\mathscr D$-classes. We also apply our results to determine the number of idempotent basis elements in the finite dimensional partition, Brauer and partial Brauer algebras.
A bijective topological recursion for maps
该研究双射证明任意拓扑图的递归切除公式，扩展至带自回避环模型的图和填充图，为拓扑递归项赋予组合意义，构造基于迭代 Tutte 算法，提供 Mirzakhani-McShane 恒等式的图类似物。
Exact and asymptotic enumeration of unrestricted binary phylogenetic networks through automorphism weights
本文通过自同构权重对无限制二元系统发育网络进行精确与渐近计数，提出递归方法，给出k≤5的闭式计数，并证明非树-子网络占比及随机网络非平凡自同构概率的渐近结果。
Path Enumeration by Position-Visit Counts in Recombining Trinomial Trees
针对重组三叉树路径枚举复杂度高的问题，提出质量平移枚举算法，利用对称性将搜索空间指数级缩减，推导并验证了算法代价下界，还揭示其与带细化的Motzkin路径的结构关联。
Various lattice path models are reviewed. The enumeration is done using generating functions. A few bijective considerations are woven in as well. The kernel method is often used. Computer algebra was an essential tool. Some results are new, some have appeared before. The lattice path models we treated, are: Hoppy's walks, the combinatorics of sequence A002212 in \cite{OEIS} (skew Dyck paths, Schröder paths, Hex-trees, decorated ordered trees, multi-edge trees, etc.) Weighted unary-binary trees also occur, and we could improve on our old paper on Horton-Strahler numbers \cite{FlPr86}, by using…
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