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

Terms

a(0) =0a(1) =20a(2) =52a(3) =116a(4) =180a(5) =308a(6) =372a(7) =564a(8) =692a(9) =884a(10) =1012a(11) =1332a(12) =1460a(13) =1844a(14) =2036a(15) =2292a(16) =2548a(17) =3060a(18) =3252a(19) =3828a(20) =4084a(21) =4468a(22) =4788a(23) =5492a(24) =5748a(25) =6388a(26) =6772a(27) =7348a(28) =7732a(29) =8628