Number DL's in all skew Dyck paths of semilength n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =5a(4) =23a(5) =106a(6) =493a(7) =2312a(8) =10917a(9) =51840a(10) =247319a(11) =1184557a(12) =5692517a(13) =27434578a(14) =132547877a(15) =641789941a(16) =3113487683a(17) =15130119784a(18) =73637665027a(19) =358883327591