Akm[k_,m_]:=Piecewise[{{A[0, 0], k == 0 && m == 0}, {(-I)*A[2, 1], k == 2 && m == -2}, {(-1 - I)*A[2, 1], k == 2 && m == -1}, {(1 - I)*A[2, 1], k == 2 && m == 1}, {I*A[2, 1], k == 2 && m == 2}, {Sqrt[5/14]*A[4, 0], k == 4 && (m == -4 || m == 4)}, {(-1 + I)*Sqrt[7]*A[4, 1], k == 4 && m == -3}, {(2*I)*Sqrt[2]*A[4, 1], k == 4 && m == -2}, {(-1 - I)*A[4, 1], k == 4 && m == -1}, {A[4, 0], k == 4 && m == 0}, {(1 - I)*A[4, 1], k == 4 && m == 1}, {(-2*I)*Sqrt[2]*A[4, 1], k == 4 && m == 2}, {(1 + I)*Sqrt[7]*A[4, 1], k == 4 && m == 3}, {(-I/33)*(8*Sqrt[22]*A[6, 1] - Sqrt[55]*B[6, 2]), k == 6 && m == -6}, {((-1 - I)*(A[6, 1] + 2*Sqrt[10]*B[6, 2]))/Sqrt[66], k == 6 && m == -5}, {-(Sqrt[7/2]*A[6, 0]), k == 6 && (m == -4 || m == 4)}, {(1/6 - I/6)*(Sqrt[10]*A[6, 1] - 4*B[6, 2]), k == 6 && m == -3}, {(-I)*B[6, 2], k == 6 && m == -2}, {(-1 - I)*A[6, 1], k == 6 && m == -1}, {A[6, 0], k == 6 && m == 0}, {(1 - I)*A[6, 1], k == 6 && m == 1}, {I*B[6, 2], k == 6 && m == 2}, {(-1/6 - I/6)*(Sqrt[10]*A[6, 1] - 4*B[6, 2]), k == 6 && m == 3}, {((1 - I)*(A[6, 1] + 2*Sqrt[10]*B[6, 2]))/Sqrt[66], k == 6 && m == 5}, {(I/33)*(8*Sqrt[22]*A[6, 1] - Sqrt[55]*B[6, 2]), k == 6 && m == 6}}, 0]