a(n) = A027170(2n, n-2).

Terms

a(0) =9a(1) =58a(2) =264a(3) =1106a(4) =4495a(5) =18014a(6) =71652a(7) =283760a(8) =1120806a(9) =4419928a(10) =17413572a(11) =68569666a(12) =269941451a(13) =1062631046a(14) =4183370636a(15) =16471711736a(16) =64870158866a(17) =255541666976