Rational solutions of the fourth and fifth Painlev\'{e} hierarchies
  We will consider four hierarchies of higher order analogues of the fourth (P4) and fifth (P5) Painleve equations. The necessary and sufficient conditions for having rational solutions will be presented. Further we well consider two more hierarchies of the (P4). We well show that both of them admit the solution in the form of $1/x$. The last result shows that all the considered P4-hierarchies have the common property: they assume the solution $1/x$ as also the original P4 does. 
Anton Grigor'ev
math.CA