Nonautonomous Riccati difference equation with real $k$-periodic ($k\geq   1$) coefficients
  We study the non-autonomous Riccati difference equation \[x_{n+1}=\frac{a_nx_n+b_n}{c_nx_n+d_n}, \ n=0,1,2,\cdots\] where $(a_n)_{n\geq0}, \ (b_n)_{n\geq0}, \ (c_n)_{n\geq0}, \ \text{and} \ (d_n)_{n\geq0}$ are $k$-periodic sequences, $k\geq 1$, with initial value $x_0 \in \mathbb{R}$. Precisely we give a detailed analysis of the forbidden set and the character of the solutions. 
Raouf Azizi
math.DS