Nonlocal symmetries and integrable ordinary differential equations: xuml+3xx center dot+x(3)=0 and its generalizations

The equation xuml+3xx center dot+x(3)=0 is well known in many areas of mathematics and physics. It possesses the algebra sl(3,R) of Lie point symmetries, hence is equivalent to the equation for a free particle, and both left and right Painleveacute series. We investigate two higher-dimensional analogs in terms of their symmetry and singularity structures. We find a drastic reduction in symmetry and a loss of some of the singularity properties. From the nonlocal symmetries we are able to determine the complete symmetry group as being represented by a five-dimensional Abelian algebra.