2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/62155We count tilings of a rectangle of integer sides m-1 and n-1 by a special set of tiles. The result is obtained fron the study of the kernel of the adjacency matrix of an n x n rectangular graph of Z x Z.13 pages, 25 figuresCombinatorics05B45, 05C50text