a(n) = T(2n,n+4), T given by A026736.

Terms

a(0) =1a(1) =10a(2) =66a(3) =365a(4) =1837a(5) =8741a(6) =40133a(7) =179932a(8) =793605a(9) =3460106a(10) =14961664a(11) =64306917a(12) =275180827a(13) =1173714565a(14) =4994096327a(15) =21211537533a(16) =89972566673a(17) =381261067469