magma:// Please install CHIMP (https://github.com/edgarcosta/CHIMP) if you want to run this code
chi := DirichletCharacter("392.57");
S:= CuspForms(chi, 2);
N := Newforms(S);
sage:from sage.modular.dirichlet import DirichletCharacter
H = DirichletGroup(392, base_ring=CyclotomicField(14))
chi = DirichletCharacter(H, H._module([0, 0, 12]))
N = Newforms(chi, 2, names="a")
This newform subspace can be constructed as the kernel of the linear operator
\( T_{3}^{42} - 5 T_{3}^{41} + 24 T_{3}^{40} - 78 T_{3}^{39} + 291 T_{3}^{38} - 818 T_{3}^{37} + \cdots + 3265249 \)
acting on \(S_{2}^{\mathrm{new}}(392, [\chi])\).