Number of 2 X 2 matrices having all elements in {0,1,...,n} and determinant = 1 (mod 3).

Terms

a(0) =0a(1) =3a(2) =24a(3) =52a(4) =164a(5) =384a(6) =592a(7) =1131a(8) =1944a(9) =2628a(10) =4128a(11) =6144a(12) =7744a(13) =10955a(14) =15000a(15) =18100a(16) =23988a(17) =31104a(18) =36432a(19) =46179a(20) =57624a(21) =66052a(22) =81056a(23) =98304a(24) =110848a(25) =132723a(26) =157464a(27) =175284a(28) =205860a(29) =240000