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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