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

Terms

a(0) =0a(1) =1a(2) =8a(3) =23a(4) =46a(5) =77a(6) =120a(7) =167a(8) =230a(9) =301a(10) =384a(11) =463a(12) =590a(13) =685a(14) =808a(15) =959a(16) =1118a(17) =1245a(18) =1448a(19) =1591a(20) =1830a(21) =2053a(22) =2256a(23) =2431a(24) =2766a(25) =3005a(26) =3248a(27) =3535a(28) =3886a(29) =4109