T(2n+3,n), where T is the array in A055830.

Terms

a(0) =3a(1) =15a(2) =73a(3) =361a(4) =1806a(5) =9122a(6) =46425a(7) =237721a(8) =1223365a(9) =6321965a(10) =32784830a(11) =170528190a(12) =889291352a(13) =4648068192a(14) =24342384337a(15) =127707864849a(16) =671047979300