Spherical growth series for modular group.

Terms

a(0) =1a(1) =3a(2) =4a(3) =6a(4) =8a(5) =12a(6) =16a(7) =24a(8) =32a(9) =48a(10) =64a(11) =96a(12) =128a(13) =192a(14) =256a(15) =384a(16) =512a(17) =768a(18) =1024a(19) =1536a(20) =2048a(21) =3072a(22) =4096a(23) =6144a(24) =8192a(25) =12288a(26) =16384a(27) =24576a(28) =32768a(29) =49152