Why is the process not markov ? I wrote out Xn+1 = Zn+1 + c Zn + c2 Zn-1 + c3 Zn-2 and Xn = Zn+ c1 Zn-1+ c2 Zn-2+ c3 Zn-3 and noticed all the Z's needed to compute Xn+1 were included in Xn except Zn+1. So given Xn i take no Z's from Xn-1 , Xn-2 ,...