0,3

Table of n, a(n) for n=0..18.

For n=4 the paths UUUDDUDD and UUDUUDDD fail the definition because {2,2} != {3,1} so a(4) = 12 rather than Catalan(4)=14.

Sequence in context: A101785 A003089 A213263 * A182488 A261788 A112412

Adjacent sequences: A179541 A179542 A179543 * A179545 A179546 A179547

nonn,more

David Scambler, Jan 08 2011

a(15)-a(18) from Alois P. Heinz, May 07 2012

approved