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 A045615 Number of level n genus 0 subgroups of PSL(2,Z) up to conjugacy. 0
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified May 26 02:10 EDT 2024. Contains 372807 sequences. (Running on oeis4.)