G.f.: 8/(3 + 5*sqrt(1-16*x)).

Terms

a(0) =1a(1) =5a(2) =45a(3) =485a(4) =5725a(5) =71445a(6) =925965a(7) =12335685a(8) =167817405a(9) =2321105525a(10) =32536755565a(11) =461181239205