2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/65646A connection between permutations that avoid 4231 and a certain queueing discipline is established. It is proved that a more restrictive queueing discipline corresponds to avoiding both 4231 and 42513, and enumeration results for such permutations are given.6 pages, no figuresCombinatorics05A05text