منابع مشابه
Counting 1324-Avoiding Permutations
We consider permutations that avoid the pattern 1324. By studying the generating tree for such permutations, we obtain a recurrence formula for their number. A computer program provides data for the number of 1324-avoiding permutations of length up to 20.
متن کاملCounting (3 + 1)-avoiding Permutations
Aposet is (3+1)-free if it contains no induced subposet isomorphic to the disjoint union of a 3-element chain and a 1-element chain. These posets are of interest because of their connection with interval orders and their appearance in the (3 + 1)-free Conjecture of Stanley and Stembridge. The dimension 2 posets P are exactly the ones which have an associated permutation π where i ≺ j in P if an...
متن کاملCounting 1324, 4231-Avoiding Permutations
Classes of permutations are sets of permutations that are closed downwards under taking subpermutations. They are usually presented as sets C that avoid a given set B of permutations (i.e. the permutations of C have no subpermutation in the set B). We express this by the notation C = Av(B). Much of the inspiration for elucidating the structure of pattern classes has been driven by the enumerati...
متن کاملCounting Stabilized-Interval-Free Permutations
A stabilized-interval-free (SIF) permutation on [n] = {1, 2, ..., n} is one that does not stabilize any proper subinterval of [n]. By presenting a decomposition of an arbitrary permutation into a list of SIF permutations, we show that the generating function A(x) for SIF permutations satisfies the defining property: [xn−1]A(x)n = n! . We also give an efficient recurrence for counting SIF permut...
متن کاملCounting subwords in flattened permutations
In this paper, we consider the number of occurrences of descents, ascents, 123-subwords, 321-subwords, peaks and valleys in flattened permutations, which were recently introduced by Callan in his study of finite set partitions. For descents and ascents, we make use of the kernel method and obtain an explicit formula (in terms of Eulerian polynomials) for the distribution on Sn in the flattened ...
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory, Series A
سال: 1980
ISSN: 0097-3165
DOI: 10.1016/0097-3165(80)90012-6