The modular curve $X_{31}$

Curve name $X_{31}$
Index $12$
Level $8$
Genus $0$
Does the subgroup contain $-I$? Yes
Generating matrices $ \left[ \begin{matrix} 1 & 1 \\ 2 & 1 \end{matrix}\right], \left[ \begin{matrix} 1 & 3 \\ 6 & 7 \end{matrix}\right], \left[ \begin{matrix} 1 & 0 \\ 0 & 7 \end{matrix}\right]$
Images in lower levels
LevelIndex of imageCorresponding curve
$2$ $3$ $X_{6}$
$4$ $6$ $X_{12}$
Meaning/Special name
Chosen covering $X_{12}$
Curves that $X_{31}$ minimally covers $X_{12}$
Curves that minimally cover $X_{31}$ $X_{129}$, $X_{145}$
Curves that minimally cover $X_{31}$ and have infinitely many rational points.
Model \[\mathbb{P}^{1}, \mathbb{Q}(X_{31}) = \mathbb{Q}(f_{31}), f_{12} = \frac{2}{f_{31}^{2}}\]
Info about rational points None
Comments on finding rational points None
Elliptic curve whose $2$-adic image is the subgroup $y^2 = x^3 - x^2 - 28x - 12$, with conductor $2312$
Generic density of odd order reductions $3331/10752$

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