  We study a) the limit of the ratio of two consecutive terms in such a
sequence and b) the limit of the ratio of two terms in which one has a lag
equal to 2. In the general case limit a) does not exist but we have two
limiting values depending on the parity of the index. And these limits depend
on the initial conditions. Limit b) exists and does not depend on the the
initial conditions. Finally we seek the set of initial conditions for which
this limit exists (that is, the two limiting values coincide) and obtain this
limit.
