Mathematical Institute of the Serbian Academy of Science, Knez Mihailova 35/I, Beograd 11000, Serbia
Copyright © 2007 Stevo Stević. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
We show that the difference equation , , where , is periodic with period 4 if and only if for some positive constants or if when and if , with . Also, we prove that the difference equation , , where , is periodic with period 5 if and only if , for some positive constants .