a(n) = T(2n, n-2), T given by A026758.

Terms

a(0) =1a(1) =8a(2) =48a(3) =259a(4) =1328a(5) =6622a(6) =32483a(7) =157739a(8) =761128a(9) =3657815a(10) =17534231a(11) =83925062a(12) =401363296a(13) =1918822635a(14) =9173429111a(15) =43866599736a(16) =209853869150