2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/218205We characterise and enumerate permutations that are sortable by n-4 passes through a stack. We conjecture the number of permutations sortable by n-5 passes, and also the form of a formula for the general case n-k, which involves a polynomial expression.6 pagesCombinatoricstext