Two Bijections for Dyck Path Parameters

Here we give two bijections, one to show that the number of UUU-free Dyck n-paths is the Motzkin number M_n, the other to obtain the (known) distributions of the parameters ''number of UDUs'' and ''number of DDUs'' on Dyck n-paths. The first bijection is straightforward, the second not quite so obvious.

LaTeX dvi ps pdf