Number of 2 X 2 matrices having all terms in {-n,...,0,..,n} and positive determinant.

Terms

a(0) =24a(1) =248a(2) =1056a(3) =3008a(4) =6904a(5) =13624a(6) =24448a(7) =40576a(8) =63640a(9) =95288a(10) =137632a(11) =192384a(12) =262392a(13) =349688a(14) =457088a(15) =587520a(16) =744344a(17) =930104a(18) =1149152a(19) =1404160a(20) =1699640a(21) =2039544a(22) =2428352a(23) =2869312a(24) =3368472a(25) =3929912a(26) =4558688a(27) =5259712a(28) =6039480