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

Terms

a(0) =0a(1) =5a(2) =33a(3) =112a(4) =288a(5) =605a(6) =1145a(7) =1968a(8) =3176a(9) =4861a(10) =7161a(11) =10152a(12) =14040a(13) =18917a(14) =24961a(15) =32352a(16) =41312a(17) =51949a(18) =64585a(19) =79320a(20) =96472a(21) =116277a(22) =139025a(23) =164840a(24) =194184a(25) =227261a(26) =264385a(27) =305840a(28) =352096a(29) =403245