2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/103639We prove that the set of permutations generated by a stack of depth two and an infinite stack in series has a basis (defining set of forbidden patterns) consisting of 20 permutations of length 5, 6, 7 and 8. We prove this via a ``canonical'' generating algorithm.14 pages, 6 figures, 2 tables. To appear in Electronic Journal of CombinatoricsCombinatorics05A05text