[seqfan] A006149, A006150 and A006151 all titled "Number of Dyck paths"

[David Scambler]

Please, can anyone pin down a more precise definition of "Dyck path" as used for these sequences?

The references given are:

S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, 
Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 183).

M. de Sainte-Catherine, Couplages et Pfaffiens en Combinatoire. Phys-ique 
et Informatique. Ph.D Dissertation, Universit\'{e} Bordeaux I, 1983.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
Academic Press, 1995 (includes this sequence). 


Thanks
dave