Abstract
We show that in the extended modular group $\overline \Gamma = \rm {PGL}(2, \mathbb {Z})$ there are exactly seven finite subgroups up to conjugacy; three subgroups of size 2, one subgroup each of size 3, 4, and 6, and the trivial subgroup of size 1.
Citation
Gregory Dresden. Prakriti Panthi. Anukriti Shrestha. Jiahao Zhang. "Finite subgroups of the extended modular group." Rocky Mountain J. Math. 49 (4) 1123 - 1127, 2019. https://doi.org/10.1216/RMJ-2019-49-4-1123
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