T(2n,n), array T as in A054120.

Terms

a(0) =1a(1) =3a(2) =18a(3) =114a(4) =750a(5) =5058a(6) =34692a(7) =240852a(8) =1687446a(9) =11906610a(10) =84490428a(11) =602335836a(12) =4310670156a(13) =30950436468a(14) =222844189320