T(n,n-2), where T is the array in A026148.

Terms

a(0) =1a(1) =2a(2) =7a(3) =20a(4) =60a(5) =176a(6) =517a(7) =1512a(8) =4415a(9) =12870a(10) =37477a(11) =109044a(12) =317109a(13) =921870a(14) =2679510a(15) =7787904a(16) =22636503a(17) =65804638a(18) =191332945a(19) =556456060a(20) =1618813834a(21) =4710869108a(22) =13713658368a(23) =39935698400a(24) =116340344575a(25) =339050396646a(26) =988474306017