T(2n,n-2), T given by A026692.

Terms

a(0) =1a(1) =6a(2) =48a(3) =200a(4) =1324a(5) =5220a(6) =32590a(7) =126829a(8) =771933a(9) =2996761a(10) =18000452a(11) =69937236a(12) =416889740a(13) =1622747113a(14) =9626951158a(15) =37552445443a(16) =222077315939a(17) =868086752186