2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/77296We 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'.AMSTeXCombinatoricstext