Number of skew Dyck paths of semilength n with no base pyramids.

Terms

a(0) =1a(1) =0a(2) =1a(3) =5a(4) =19a(5) =73a(6) =292a(7) =1203a(8) =5065a(9) =21697a(10) =94274a(11) =414514a(12) =1840981a(13) =8247011a(14) =37220261a(15) =169079113a(16) =772489020a(17) =3547371679a(18) =16364309243a(19) =75799327800a(20) =352402156770