magma://Please install CHIMP (https://github.com/edgarcosta/CHIMP) if you want to run this code
chi := DirichletCharacter("71.1");
S:= CuspForms(chi, 8);
N := Newforms(S);
sage:from sage.modular.dirichlet import DirichletCharacter
H = DirichletGroup(71, base_ring=CyclotomicField(2))
chi = DirichletCharacter(H, H._module([0]))
N = Newforms(chi, 8, names="a")
This newform subspace can be constructed as the kernel of the linear operator
\( T_{2}^{24} - 2445 T_{2}^{22} + 2581812 T_{2}^{20} - 239600 T_{2}^{19} - 1543388120 T_{2}^{18} + \cdots + 96\!\cdots\!24 \)
acting on \(S_{8}^{\mathrm{new}}(\Gamma_0(71))\).