Classical Hecke eigenforms for $\Gamma_0(p)$.

I am in need of classical eigenforms for $\Gamma_0(p)$.

In particular I need these to be newforms for each of the even weights 8 to 26 and would settle just for cases $p=2,3$ at this moment in time. I need them in a format from which I am able to find critical L-values.

Does anyone know where to find these and/or whether MAGMA/Maple/PARI is able to compute them? (The online documentation for MAGMA doesn't seem to mention commands for finding eigen-bases)

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perhaps that Stein's tables or links at the end will help you... – Raymond Manzoni Jul 22 '12 at 11:34
William Stein's lectures Explicitly Computing Modular Forms could perhaps help you too (around page 50). William Stein is maintaining Sage (that includes Pari/Maxima and other free software...) – Raymond Manzoni Jul 22 '12 at 11:47