2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145259Let U and V be two Bertrand numeration systems, and, a and b the two Parry numbers there are naturally associated with. Suppose they are multiplicatively independent. We prove that, if E is a subset of positive integers which is both U and V recognizable, then E is a finite union of arithmetical progressions.Number TheoryCombinatorics11B85text