T(2n,n-2), T given by A026714.

Terms

a(0) =1a(1) =9a(2) =59a(3) =346a(4) =1931a(5) =10513a(6) =56478a(7) =301128a(8) =1598424a(9) =8461783a(10) =44720274a(11) =236094725a(12) =1245579365a(13) =6568448233a(14) =34627898410a(15) =182517293169a(16) =961887614156