Number of equivalence classes of ballot paths of length n for the string dud.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =5a(7) =7a(8) =11a(9) =16a(10) =26a(11) =39a(12) =63a(13) =95a(14) =154a(15) =235a(16) =381a(17) =585a(18) =948a(19) =1464a(20) =2373a(21) =3682a(22) =5967a(23) =9293a(24) =15060a(25) =23531a(26) =38131a(27) =59741a(28) =96801a(29) =152020