a(n) = A192942(n)/2.

Terms

a(0) =0a(1) =1a(2) =5a(3) =31a(4) =224a(5) =1844a(6) =17028a(7) =174284a(8) =1958176a(9) =23959760a(10) =317128240a(11) =4514617360a(12) =68784608640