A045615 Number of level n genus 0 subgroups of PSL(2,Z) up to conjugacy.

1, 3, 4, 7, 8, 12, 11, 18, 10, 7, 2, 11, 3, 4, 4, 9, 0, 6, 0, 1, 2, 0, 0, 1, 2, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

1,2

Links

Table of n, a(n) for n=1..85.

David A. Cox and Walter R. Parry, Genera of congruence subgroups in Q-quaternion algebras, Journal für die reine und angewandte Mathematik, Vol. 351 (1984) pp. 66-112.

Formula

a(n) = 0 for n > 48 [from Cox and Parry]. - Sean A. Irvine, Mar 14 2021

Crossrefs

Sequence in context: A343151 A014602 A078823 * A211220 A051201 A026449

Adjacent sequences: A045612 A045613 A045614 * A045616 A045617 A045618

Keyword

nonn,easy

Author

John McKay (mckay(AT)cs.concordia.ca)

Extensions

More terms from Sean A. Irvine, Mar 14 2021

Status

approved