Number of skew Dyck paths of semilength n with no UDL's.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =71a(6) =262a(7) =994a(8) =3852a(9) =15183a(10) =60686a(11) =245412a(12) =1002344a(13) =4129012a(14) =17135432a(15) =71575350a(16) =300690836a(17) =1269662127a(18) =5385593406a(19) =22938095326a(20) =98059308676a(21) =420610907183