a(n) = T(2n+1,n), array T as in A055818.

Terms

a(0) =1a(1) =5a(2) =24a(3) =122a(4) =640a(5) =3422a(6) =18536a(7) =101362a(8) =558336a(9) =3093302a(10) =17218168a(11) =96214890a(12) =539415552a(13) =3032659086a(14) =17091411912a(15) =96527966178a(16) =546184965120