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%I #20 Sep 02 2023 11:27:40
%S 1,1,2,2,1,8,4,5,12,12,7,48,24,35,75,80,37,269,114,193,404,359,174,
%T 1357,519,722,1664,1784,776,4995,2054
%N Number of passports of index n subgroups in PSL_2 (ZZ).
%C The passports are defined as the conjugacy classes of index n subgroups in PSL_2 (ZZ) modulo the ramification degrees of the covering maps and the monodromy groups.
%H D. Berghaus, H. Monien and D. Radchenko, <a href="https://arxiv.org/abs/2301.02135">A Database of Modular Forms on Noncongruence Subgroups</a>, arXiv:2301.02135 [math.NT], 2023.
%H D. Berghaus, H. Monien and D. Radchenko, <a href="https://github.com/David-Berghaus/psl2z_db">A database of subgroups of PSL(2,ℤ)</a> (2023).
%Y Cf. A121350, A005133.
%K nonn,more
%O 1,3
%A _David Berghaus_, Feb 06 2023
%E Corrected by _David Berghaus_, Sep 02 2023