Agraïments: DPI2008-06699-C02-02 and DPI2011-25822

This paper studies non-autonomous Lyness type recurrences of the form xn+2 =(an +xn+1)/xn, where {an} is a k-periodic sequence of positive numbers with primitive period k. We show that for the cases k ∈ {1, 2, 3, 6} the behavior of the sequence {xn} is simple (integrable) while for the remaining cases satisfying this behavior can be much more complicated (chaotic). We also show that the cases where k is a multiple of 5 present some different features.