Abstract
Let $G = \Gamma_0(N)$ and $g$ be the group generated by the involution $z \mapsto -1/Nz$ of the upper half plane. We determine the cohomology set $H^1(g,G)$ in terms of the class numbers $h(-N)$ and $h(-4N)$ of quadratic forms.
Citation
Takashi Ono. "On certain cohomology set for $\Gamma _0(N)$. II." Proc. Japan Acad. Ser. A Math. Sci. 77 (7) 108 - 110, Sept. 2001. https://doi.org/10.3792/pjaa.77.108
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