How would you prove this? [math]W_n (z)=1+\exp\left (\dfrac {i}{2\pi}\displaystyle\int_0^{\infty}\dfrac {\frac {(2n-1)i\pi+t+\ln (z)-\ln (t)}{(2n+1)i\pi+t+\ln (z)-\ln (t)}}{1+t}\mathrm {d}t\right)\left (-1+2ni\pi+\ln (z)\right)[/math]
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