Consider a process $\{X_n, n\geq 0\}$ with state space $S=\{0,1,2\}$ s.t. $$ P(X_{n+1}=j | X_n=i, X_{n-1}=i_{n-1}, \dots, X_0=i_0)=\begin{cases} P_{ij}^I \ \ \ n \ \mbox{ even},\\ P_{ij}^{II} \ \ \ n \ \mbox{odd} \end{cases} $$where $\sum_{j=0}^2 P_{ij}^I = \sum_{j=0}^2 P_{ij}^{II}=1$.
I don't see why this shouldn't be a Markov chain. It looks to me like a non-time homogeneous Markov chain.
Any ideas? Thanks a lot for any help! :)
Each inhomogenous Markov chain $(X_n)_{n\geqslant0}$ on the state space $S$ with transitions $(P^I_{ij})_{ij}$ and $(P^{II}_{ij})_{ij}$ alternatively, can be embedded in a homogenous Markov chain $(Z_n)_{n\geqslant0}$ with $Z_n=(X_n,Y_n)$, on the state space $S\times\{0,1\}$, with transitions $(Q_{(i,u),(j,v)})_{(i,u),(j,v)}$ defined by $$ Q_{(i,0),(j,1)}=P^I_{ij},\quad Q_{(i,1),(j,0)}=P^{II}_{ij},\quad Q_{(i,0),(j,0)}=Q_{(i,1),(j,1)}=0. $$