2 Einar Steingrímsson and Lauren
نویسندگان
چکیده
منابع مشابه
Permutation tableaux and permutation patterns
Lauren Williams (joint work with Einar Steingrímsson) We introduce and study a class of tableaux which we call permutation tableaux; these tableaux are naturally in bijection with permutations, and they are a distinguished subset of the " Le-diagrams " of Alex Postnikov. The structure of these tableaux is in some ways more transparent than the structure of permutations; therefore we believe tha...
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An occurrence of a classical pattern p in a permutation π is a subsequence of π whose letters are in the same relative order (of size) as those in p. In an occurrence of a generalized pattern, some letters of that subsequence may be required to be adjacent in the permutation. Subsets of permutations characterized by the avoidance—or the prescribed number of occurrences— of generalized patterns ...
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Ascent sequences are sequences of nonnegative integers with restrictions on the size of each letter, depending on the number of ascents preceding it in the sequence. Ascent sequences have recently been related to (2+2)-free posets and various other combinatorial structures. We study pattern avoidance in ascent sequences, giving several results for patterns of lengths up to 4, for Wilf equivalen...
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The study of Genocchi numbers, it is claimed, goes back to Euler. In what sense that is true is somewhat unclear, but during the last two or three decades the Genocchi numbers have been studied by Dumont and some collaborators [2–7]. In recent years there has been a flurry of activity in this field, viz. [1, 9–13]. The Genocchi numbers are cousins to the Euler numbers which count the alternatin...
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We introduce a generalization of the classical game of Nim by placing the piles on the vertices of a simplicial complex and allowing a move to affect the piles on any set of vertices that forms a face of the complex. Under certain conditions on the complex we present a winning strategy. These conditions are satisfied, for instance, when the simplicial complex consists of the independent sets of...
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تاریخ انتشار 2007