Results 71 to 80 of about 152 (126)

TO TEACH COMBINATORICS, USING SELECTED PROBLEMS [PDF]

, 2012
In 1972, professor Grigore Moisil, the most famous Romanian academician for Mathematics, said about Combinatorics, that it is “an opportunity of a renewed gladness”, because “each problem in the domain asks for its solving, an expenditure without any ...
Modan, Laurentiu
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Boolean elements in the Bruhat order [PDF]

We show that a Weyl group element is boolean if and only if it avoids a set of Billey-Postnikov patterns, which we describe explicitly. Our proof is based on analysis of inversion sets, and it is in large part type-uniform.
Gao, Yibo, Hänni, Kaarel
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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
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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
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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
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Decompositions of packed words and self duality of Word Quasisymmetric Functions [PDF]

By Foissy's work, the bidendriform structure of the Word Quasisymmetric Functions Hopf algebra (WQSym) implies that it is isomorphic to its dual. However, the only known explicit isomorphism due to Vargas does not respect the bidendriform structure. This
Mlodecki, Hugo
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The 26 Wilf-equivalence classes of length five quasi-consecutive patterns [PDF]

Discrete Mathematics & Theoretical Computer Science, 2018
We present two families of Wilf-equivalences for consecutive and quasi-consecutive vincular patterns. These give new proofs of the classification of consecutive patterns of length $4$ and $5$.
Evan Chen, Shyam Narayanan
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Key-avoidance for alternating sign matrices [PDF]

Discrete Mathematics & Theoretical Computer Science
We initiate a systematic study of key-avoidance on alternating sign matrices (ASMs) defined via pattern-avoidance on an associated permutation called the \emph{key} of an ASM.
Mathilde Bouvel, Rebecca Smith, Jessica Striker   +2 more
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Convexity of tableau sets for type A Demazure characters (key polynomials), parabolic Catalan numbers [PDF]

Discrete Mathematics & Theoretical Computer Science, 2018
This is the first of three papers that develop structures which are counted by a "parabolic" generalization of Catalan numbers. Fix a subset R of {1,..,n-1}. Consider the ordered partitions of {1,..,n} whose block sizes are determined by R. These are the
Robert A. Proctor, Matthew J. Willis
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Математическо моделиране при дизайна на тъкачни структури [PDF]

, 2010
Красимир Йорджев, Христина Костадинова - В работата се разглежда една релация на еквивалентност в множеството от всички квадратни бинарни матрици. Обсъдена е комбинаторната задача за намиране мощността и елементите на фактормножеството относно тази ...
Kostadinova, Hristina, Yordzhev, Krasimir   +1 more
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