## Estimation and limit of analytic function

Hi,

I've the following estimation:

$|c_n| \leq (\log||\phi||+||a||r)\frac{2}{r^n}$

where

$c_n=\frac{1}{\pi i} \int_{|\lambda|=r}\log|\psi (\lambda)|\frac{d\lambda}{\lambda^{n+1}}$,

$\phi(x+\alpha e)=\alpha$

$\psi(\lambda)=\phi[exp(\lambda a)]$.

My questions is: Why $c_n=0$ for $n \geq 2$?