2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123409A pattern class is a set of permutations closed under the formation of subpermutations. Such classes can be characterised as those permutations not involving a particular set of forbidden permutations. A simple collection of necessary and sufficient conditions on sets of forbidden permutations which ensure that the associated pattern class is of polynomial growth is determined. A catalogue of all such sets of forbidden permutations having three or fewer elements is provided together with bounds on the degrees of the associated enumerating polynomials.17 pages, 4 figuresCombinatorics05A15 (Primary), 05A05 (Secondary)text