a(n) = A027144(2n, n-2).

Terms

a(0) =1a(1) =12a(2) =56a(3) =480a(4) =2040a(5) =16576a(6) =69888a(7) =557568a(8) =2361600a(9) =18675712a(10) =79613952a(11) =626409472a(12) =2686867456a(13) =21071708160a(14) =90875494400a(15) =711081984000