Number of cusps of principal congruence subgroup Gamma^{hat}(n).

Terms

a(0) =3a(1) =4a(2) =6a(3) =12a(4) =12a(5) =24a(6) =24a(7) =36a(8) =36a(9) =60a(10) =48a(11) =84a(12) =72a(13) =96a(14) =96a(15) =144a(16) =108a(17) =180a(18) =144a(19) =192a(20) =180a(21) =264a(22) =192a(23) =300a(24) =252a(25) =324a(26) =288a(27) =420a(28) =288a(29) =480