T(n,n-2), array T as in A047140.

Terms

a(0) =1a(1) =4a(2) =13a(3) =42a(4) =148a(5) =540a(6) =1945a(7) =6994a(8) =25784a(9) =96564a(10) =361560a(11) =1353608a(12) =5113044a(13) =19462184a(14) =74227737a(15) =283335006a(16) =1085696746a(17) =4176869836a(18) =16100775648a(19) =62132631186a(20) =240258482330a(21) =931152718588