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

Terms

a(0) =1a(1) =13a(2) =50a(3) =120a(4) =244a(5) =410a(6) =681a(7) =981a(8) =1431a(9) =1948a(10) =2623a(11) =3315a(12) =4373a(13) =5323a(14) =6588a(15) =8009a(16) =9706a(17) =11290a(18) =13535a(19) =15503a(20) =18233a(21) =20912a(22) =23879a(23) =26725a(24) =30910a(25) =34443a(26) =38556a(27) =42887a(28) =48041a(29) =52519