1 (-k^2 + 8*(-1 + Sqrt[1 + k^2/(c - I*k0)^2])*(c - I*k0)^2 - 12*(-1 + Sqrt[1 + k^2/(2*c - I*k0)^2])*(2*c - I*k0)^2 + 8*(-1 + Sqrt[1 + k^2/(3*c - I*k0)^2])*(3*c - I*k0)^2 - 2*(-1 + Sqrt[1 + k^2/(4*c - I*k0)^2])*(4*c - I*k0)^2 + k^2*Sqrt[Pi]*(I*Piecewise[{{0, k^2/k0^2 <= 1}}, (2*k0*Sqrt[k^2 - k0^2])/(k^2*Sqrt[Pi])] + Piecewise[{{(k^2 + 2*k0*(-k0 + Sqrt[-k^2 + k0^2]))/(k^2*Sqrt[Pi]), k^2/k0^2 < 1}, {(1 - (2*k0^2)/k^2)/Sqrt[Pi], k^2/k0^2 > 1}}, 0]))/(2*k^2*k0^2)
2 SeriesData[k, Infinity, {(30*c^5)/k0^2 - ((15*I)*c^4)/k0, 0, 315*c^5 - (525*c^7)/k0^2 + ((1365*I)/2*c^6)/k0 - (105*I)/2*c^4*k0, 0, (315*(370*c^9 - (729*I)*c^8*k0 - 600*c^7*k0^2 + (260*I)*c^6*k0^3 + 60*c^5*k0^4 - (6*I)*c^4*k0^5))/(16*k0^2)}, 5, 11, 1]