## The modular curve $X_{121d}$

Curve name $X_{121d}$
Index $48$
Level $16$
Genus $0$
Does the subgroup contain $-I$? No
Generating matrices $\left[ \begin{matrix} 1 & 1 \\ 8 & 1 \end{matrix}\right], \left[ \begin{matrix} 7 & 0 \\ 0 & 1 \end{matrix}\right], \left[ \begin{matrix} 5 & 5 \\ 0 & 1 \end{matrix}\right], \left[ \begin{matrix} 5 & 0 \\ 8 & 5 \end{matrix}\right]$
Images in lower levels
 Level Index of image Corresponding curve $2$ $3$ $X_{6}$ $4$ $12$ $X_{13h}$ $8$ $24$ $X_{36n}$
Meaning/Special name
Chosen covering $X_{121}$
Curves that $X_{121d}$ minimally covers
Curves that minimally cover $X_{121d}$
Curves that minimally cover $X_{121d}$ and have infinitely many rational points.
Model $\mathbb{P}^{1}$, a universal elliptic curve over an appropriate base is given by $y^2 = x^3 + A(t)x + B(t), \text{ where}$ $A(t) = -27t^{8} - 216t^{6} - 540t^{4} - 432t^{2} - 27$ $B(t) = 54t^{12} + 648t^{10} + 2916t^{8} + 6048t^{6} + 5589t^{4} + 1620t^{2} - 54$
Elliptic curve whose $2$-adic image is the subgroup $y^2 = x^3 + x^2 - 15x + 18$, with conductor $120$
Generic density of odd order reductions $47/672$