Number of Dyck paths of semilength n having no DUDU's starting at level 1.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =11a(5) =32a(6) =99a(7) =318a(8) =1051a(9) =3550a(10) =12200a(11) =42520a(12) =149930a(13) =533890a(14) =1917181a(15) =6934722a(16) =25243539a(17) =92405718a(18) =339940116a(19) =1256122632a(20) =4660081434a(21) =17350844808a(22) =64814186646a(23) =242838410652a(24) =912333763806