sage:from sage.modular.dirichlet import DirichletCharacter
H = DirichletGroup(169, base_ring=CyclotomicField(2))
chi = DirichletCharacter(H, H._module([0]))
N = Newforms(chi, 8, names="a")
magma://Please install CHIMP (https://github.com/edgarcosta/CHIMP) if you want to run this code
chi := DirichletCharacter("169.1");
S:= CuspForms(chi, 8);
N := Newforms(S);
This newform subspace can be constructed as the kernel of the linear operator
\( T_{2}^{21} - 31 T_{2}^{20} - 1568 T_{2}^{19} + 54321 T_{2}^{18} + 947492 T_{2}^{17} + \cdots + 61\!\cdots\!68 \)
acting on \(S_{8}^{\mathrm{new}}(\Gamma_0(169))\).