Sequence of Period 9 

Sequence of Period 9
11 
-3 
-8 
11 
19 
-11 
14 
11 
-3 
xn+1 = | xn | - x n-1

References:
    Amer. Math. Monthly Problem # 6439
    M. Crampin, Piecewise linear recurrence relations, Math. Gaz.