Number of elements (a b, c d) in SL(2,Z) with trace n and 0 <= a <= {b, c} <= d.

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =3a(5) =4a(6) =2a(7) =8a(8) =3a(9) =4a(10) =6a(11) =8a(12) =6a(13) =8a(14) =4a(15) =10a(16) =6a(17) =14a(18) =2a(19) =18a(20) =6a(21) =4a(22) =14a(23) =18a(24) =7a(25) =12a(26) =12a(27) =22a(28) =6a(29) =8