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

Terms

a(0) =1a(1) =10a(2) =33a(3) =152a(4) =297a(5) =528a(6) =1217a(7) =1834a(8) =2673a(9) =4744a(10) =6385a(11) =8448a(12) =13073a(13) =16506a(14) =20625a(15) =29336a(16) =35545a(17) =42768a(18) =57457a(19) =67642a(20) =79233a(21) =102152a(22) =117729a(23) =135168a(24) =168929a(25) =191530a(26) =216513a(27) =264088a(28) =295561a(29) =330000