Akm[k_,m_]:=Piecewise[{{(Ea2pp + 2*(Ee1p + Ee2p + Ee2pp))/7, k == 0 && m == 0}, {(5*(2*Ea2pp + 3*Ee1p - 5*Ee2p))/14, k == 2 && m == 0}, {(3*(3*Ea2pp + Ee1p + 3*Ee2p - 7*Ee2pp))/7, k == 4 && m == 0}, {0, k != 6 || m != 0}}, (13*(10*Ea2pp - 15*Ee1p - Ee2p + 6*Ee2pp))/70]