Expectation of $\frac{1}{x+1}$ of Poisson distribution
As the title states, I'm trying to find the expecteed value of $\frac{1}{x+1}$ where $X \sim \mathrm{Poisson}(\lambda)$
My attempt: \begin{align} &\sum \frac{1}{x+1} \cdot \frac{e^{-λ}\cdot λ^x}{x!} \\ \implies& \sum \frac{x+1}{(x+1)^2} \cdot \frac{e^{-λ}\cdot λ^x}{x!} \\ \implies& e^{-λ} \cdot \sum \frac{\lambda^{x+1}}{(x+1)!} \cdot \lambda \end{align}
I don't know how to further progress from here ... Help is appreciated
You should recognize that
$$\sum_{n=0}^{\infty} \frac{\lambda^{n+1}}{(n+1)!} = e^{\lambda}-1$$
So your result is
$$E\left ( \frac{1}{N+1}\right) = \frac{1-e^{-\lambda}}{\lambda}$$