Number of parabolic vertices of Gamma_0(n).

Terms

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