Results 71 to 80 of about 225 (160)
A refined enumeration of hex trees and related polynomials
, 2015 A hex tree is an ordered tree of which each vertex has updegree 0, 1, or 2, and an edge from a vertex of updegree 1 is either left, median, or right. We present a refined enumeration of symmetric hex trees via a generalized binomial transform.
Richard P. Stanleyb +5 more
core +1 more source
Snow Leopard Permutations and Their Even and Odd Threads [PDF]
Discrete Mathematics & Theoretical Computer Science, 2016 Caffrey, Egge, Michel, Rubin and Ver Steegh recently introduced snow leopard permutations, which are the anti-Baxter permutations that are compatible with the doubly alternating Baxter permutations. Among other things, they showed that these permutations
Eric S. Egge, Kailee Rubin
doaj +1 more source
On nested block designs geometry
Orthogonal designs, Orthogonal block structure, General balance, Commutativity of projectors, Commutative quadratic subspace, Primary 62J05, Secondary 05A15, 15A18,
Radosław Kala
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The permutation class Av(4213,2143) [PDF]
Discrete Mathematics & Theoretical Computer Science, 2017 We determine the structure of permutations avoiding the patterns 4213 and 2143. Each such permutation consists of the skew sum of a sequence of plane trees, together with an increasing sequence of points above and an increasing sequence of points to its ...
David Bevan
doaj +1 more source
Proofs of Conjectures about Pattern-Avoiding Linear Extensions [PDF]
Discrete Mathematics & Theoretical Computer Science, 2019 After fixing a canonical ordering (or labeling) of the elements of a finite poset, one can associate each linear extension of the poset with a permutation.
Colin Defant
doaj +1 more source
Growing and Destroying Catalan-Stanley Trees [PDF]
Discrete Mathematics & Theoretical Computer Science, 2018 Stanley lists the class of Dyck paths where all returns to the axis are of odd length as one of the many objects enumerated by (shifted) Catalan numbers.
Benjamin Hackl, Helmut Prodinger
doaj +1 more source
Distribution of sets of descent tops and descent bottoms on restricted permutations [PDF]
Discrete Mathematics & Theoretical Computer ScienceIn this note, we prove some and conjecture other results regarding the distribution of descent top and descent bottom sets on some pattern-avoiding permutations.
Alexander Burstein
doaj +1 more source
Enumeration of super-strong Wilf equivalence classes of permutations in the generalized factor order [PDF]
Discrete Mathematics & Theoretical Computer Science, 2019 Super-strong Wilf equivalence classes of the symmetric group ${\mathcal S}_n$ on $n$ letters, with respect to the generalized factor order, were shown by Hadjiloucas, Michos and Savvidou (2018) to be in bijection with pyramidal sequences of consecutive ...
Ioannis Michos, Christina Savvidou
doaj +1 more source
, 2002 We derive the explicit formulas of the probability generating functions of the first hitting times of simple random walks on graphs with congestion points using group representations. 2000 Mathematics Subject Classification: 60G50, 60B15, 60K30, 05A15. 1.
Mihyun Kang
core
Slit-slide-sew bijections for oriented planar maps
We construct growth bijections for bipolar oriented planar maps and for Schnyder woods. These give direct combinatorial proofs of several counting identities for these objects. Our method mainly uses two ingredients.
Éric Fusy +2 more
core +1 more source