Invariants for difference equations and systems of difference equations of rational form (Q1378690)

The author consideres the system of difference equations \[ x_{n+1} = \frac{a_n y_n + A}{x_{n-1}}, \qquad y_{n+1} = \frac{b_n x_n + A}{y_{n-1}}, n = 0, 1,\dots\tag{1} \] where the coefficients \(\{a_n\}\) and \(\{b_n\}\) are periodic sequences of positive numbers of period 2 and \(A\) is a positive constant. Some invariants for system (1) are presented. In the second part of the article, some invariants for difference equations of higher than second order are found.