The set of non-negative integer numbers, integer numbers and rational numbers are denoted respectively $ {\mathbb{N}}$ , $ {\mathbb{Z}}$ and $ {\mathbb{Q}}$ , as usual. For an integer $ n \in {\mbox{${\mathbb{Z}}$}}$ the set of the multiples of $ n$ (all of them: positive, null or negative) is denoted by $ n{\mbox{${\mathbb{Z}}$}}$ . For an integer $ n \in {\mbox{${\mathbb{Z}}$}}$ the residue class ring of the binary relation $ (a,b) \longmapsto a \equiv b \mod{n}$ is denoted by $ {\mbox{${\mathbb{Z}}$}}/n{\mbox{${\mathbb{Z}}$}}$ , as usual. For a ring $ {\mathbb{A}}$ , we denote by $ {\mbox{${\mathbb{A}}$}}[x]$ the ring of univariate polynomials in $ x$ with coefficients in $ {\mathbb{A}}$ .

Marc Moreno Maza