The Enumeration of Permutations With a Prescribed Number of ``Forbidden'' Patterns
arXiv:math/9808080
Abstract
We initiate a general approach for the fast enumeration of permutations with a prescribed number of occurrences of `forbidden' patterns, that seems to indicate that the enumerating sequence is always P-recursive. We illustrate the method completely in terms of the patterns `abc',`cab' and `abcd'.
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