2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/143772We consider a simple model of the dynamics of a single electron in a crystal lattice. Although this is a standard problem in condensed matter physics, alternative ways of evaluating a partition function for such a system lead to equalities, that may be interesting from the point of view of mathematical analysis, combinatorics and graph theory.27 pagesMathematical Physicstext