2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/168637We show that certain integral positive definite symmetric tridiagonal matrices of determinant $n$ are in one to one correspondence with elements of $(\mathbb Z/n\mathbb Z)^*$. We study some properties of this correspondence. In a somewhat unrelated second part we discuss a construction which associates a sequence of integral polytopes to every integral symmetric matrix.CombinatoricsNumber Theorytext