An application of discrete inequality to second order nonlinear oscillation (Q1336185)

The authors use the theory of discrete inequalities to obtain sufficient conditions for all solutions of the difference equation \(\Delta^ 2 y_ n + a_{n + 1} f(y_{n + 1}) = 0\), \(n \in \mathbb{N}\) with \(\Delta y_ n \equiv y_{n + 1} - y_ n\), to be oscillatory without any sign condition on \(\{a_ n\}\).