A360410 Number of passports of index n subgroups in PSL_2 (ZZ).

1, 1, 2, 2, 1, 8, 4, 5, 12, 12, 7, 48, 24, 35, 75, 80, 37, 269, 114, 193, 404, 359, 174, 1357, 519, 722, 1664, 1784, 776, 4995, 2054

Offset

1,3

Comments

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.

Links

Table of n, a(n) for n=1..31.

D. Berghaus, H. Monien and D. Radchenko, A Database of Modular Forms on Noncongruence Subgroups, arXiv:2301.02135 [math.NT], 2023.

D. Berghaus, H. Monien and D. Radchenko, A database of subgroups of PSL(2,ℤ) (2023).

Crossrefs

Cf. A121350, A005133.

Sequence in context: A357553 A246745 A111540 * A346709 A096440 A181738

Adjacent sequences: A360407 A360408 A360409 * A360411 A360412 A360413

Keyword

nonn,more

Author

David Berghaus, Feb 06 2023

Extensions

Corrected by David Berghaus, Sep 02 2023

Status

approved