Number of 2 X 2 matrices with all elements in {0,1,...,n} and determinant >=n.

Terms

a(0) =1a(1) =3a(2) =18a(3) =61a(4) =168a(5) =368a(6) =749a(7) =1310a(8) =2235a(9) =3493a(10) =5291a(11) =7640a(12) =10869a(13) =14711a(14) =19860a(15) =26051a(16) =33623a(17) =42618a(18) =53725a(19) =66280a(20) =81577a(21) =98739a(22) =118847a(23) =141800a(24) =168435a(25) =197406a(26) =231100a(27) =268595a(28) =310617a(29) =356763