sage:from sage.modular.dirichlet import DirichletCharacter
H = DirichletGroup(169, base_ring=CyclotomicField(2))
chi = DirichletCharacter(H, H._module([0]))
N = Newforms(chi, 10, 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, 10);
N := Newforms(S);
This newform subspace can be constructed as the kernel of the linear operator
\( T_{2}^{27} - 65 T_{2}^{26} - 8384 T_{2}^{25} + 596247 T_{2}^{24} + 29229748 T_{2}^{23} + \cdots - 22\!\cdots\!48 \)
acting on \(S_{10}^{\mathrm{new}}(\Gamma_0(169))\).