Using functional equations to enumerate 1324-avoiding permutations
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چکیده
We consider the problem of enumerating permutations with exactly r occurrences of the pattern 1324 and derive functional equations for this general case as well as for the pattern avoidance (r = 0) case. The functional equations lead to a new algorithm for enumerating length n permutations that avoid 1324. This approach is used to enumerate the 1324-avoiders up to n = 31. We also extend those functional equations to account for the number of inversions and derive analogous algorithms.
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تاریخ انتشار 2013