Akm[k_,m_]:=Piecewise[{{(Ea1p + Ea2p + Ea2pp + 2*Eep + 2*Eepp)/7, k == 0 && m == 0}, {(-5*(5*Ea1p + 5*Ea2p - 4*Ea2pp - 6*Eep))/28, k == 2 && m == 0}, {0, (k != 6 && (k != 4 || m != 0)) || (m != -6 && m != 0 && m != 6)}, {(3*(3*Ea1p + 3*Ea2p + 2*(3*Ea2pp + Eep - 7*Eepp)))/14, k == 4 && m == 0}, {(-13*Sqrt[33/7]*(Ea1p - Ea2p))/20, k == 6 && (m == -6 || m == 6)}}, (-13*(Ea1p + Ea2p - 20*Ea2pp + 30*Eep - 12*Eepp))/140]