T(2n,n-2), T given by A026659.

Terms

a(0) =1a(1) =8a(2) =38a(3) =202a(4) =873a(5) =4228a(6) =17982a(7) =83986a(8) =356720a(9) =1636710a(10) =6967782a(11) =31651902a(12) =135174069a(13) =610281684a(14) =2614576678a(15) =11756749378a(16) =50516489196a(17) =226522941742a(18) =975898078974