Number of skew Dyck paths of semilength n and having no LDU's.

Terms

a(0) =1a(1) =1a(2) =3a(3) =10a(4) =35a(5) =127a(6) =474a(7) =1810a(8) =7043a(9) =27839a(10) =111503a(11) =451640a(12) =1847032a(13) =7616692a(14) =31637664a(15) =132252886a(16) =555967283a(17) =2348920207a(18) =9968617393a(19) =42477135370a(20) =181661283779a(21) =779492777031