The modular curve $X_{3}$

Curve name $X_{3}$
Index $2$
Level $4$
Genus $0$
Does the subgroup contain $-I$? Yes
Generating matrices $ \left[ \begin{matrix} 3 & 3 \\ 0 & 1 \end{matrix}\right], \left[ \begin{matrix} 0 & 1 \\ 3 & 1 \end{matrix}\right]$
Images in lower levels
LevelIndex of imageCorresponding curve
$2$ $1$ $X_{1}$
Meaning/Special name Elliptic curves whose discriminant is minus a square
Chosen covering $X_{1}$
Curves that $X_{3}$ minimally covers $X_{1}$
Curves that minimally cover $X_{3}$ $X_{10}$, $X_{20}$, $X_{3a}$, $X_{3b}$
Curves that minimally cover $X_{3}$ and have infinitely many rational points. $X_{10}$, $X_{20}$, $X_{3a}$, $X_{3b}$
Model \[\mathbb{P}^{1}, \mathbb{Q}(X_{3}) = \mathbb{Q}(f_{3}), f_{1} = -f_{3}^{2} + 1728\]
Info about rational points None
Comments on finding rational points None
Elliptic curve whose $2$-adic image is the subgroup $y^2 + xy + y = x^3 + x^2 - 30x - 76$, with conductor $121$
Generic density of odd order reductions $59/112$

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