2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/73884In some previous papers we have obtained characterizations (we called them characterizations of Lambek-Carlitz type) of some class of formal power series. Now, we discuss, investigate and compare these results from a categorial point of view.7 pagesCombinatorics13Fxx ; 13F25text