Number of 2 X 2 matrices having all terms in {1,...,n} and even determinant.

Terms

a(0) =1a(1) =10a(2) =41a(3) =160a(4) =337a(5) =810a(6) =1345a(7) =2560a(8) =3761a(9) =6250a(10) =8521a(11) =12960a(12) =16801a(13) =24010a(14) =30017a(15) =40960a(16) =49825a(17) =65610a(18) =78121a(19) =100000a(20) =117041a(21) =146410a(22) =168961a(23) =207360a(24) =236497a(25) =285610a(26) =322505a(27) =384160a(28) =430081a(29) =506250