Akm[k_,m_]:=Piecewise[{{(Ea2u + 2*(Ee1u + Ee2u2 + Ee2u3))/7, k == 0 && m == 0}, {(5*(2*Ea2u + 3*Ee1u - 5*Ee2u3))/14, k == 2 && m == 0}, {(3*(3*Ea2u + Ee1u - 7*Ee2u2 + 3*Ee2u3))/7, k == 4 && m == 0}, {((13*I)/5)*Sqrt[33/14]*Me2u, k == 6 && (m == -5 || m == 5)}, {(13*(10*Ea2u - 15*Ee1u + 6*Ee2u2 - Ee2u3))/70, k == 6 && m == 0}}, 0]