One loop multiphoton helicity amplitudes

We use the solutions to the recursion relations for double-off-shell fermion currents to compute helicity amplitudes for n-photon scattering and electron-positron annihilation to photons in the massless limit of QED. The form of these solutions is simple enough to allow all of the integrations to be performed explicitly. For n-photon scattering, we find that unless $n=4$ the amplitudes for the helicity configurations (+++...+) and (-++...+) vanish to one-loop order.