# Central value of the partial exponential function [duplicate]

I need help calculating the central value of the partial exponential function :

$$\lim_{n \to \infty} e^{-n} \sum^n_{k=0} \frac{n^k}{k!}$$

fd

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## marked as duplicate by robjohn♦Mar 18 '13 at 23:17

Related to a sum of independent Poisson random variables with parameter 1 – user66322 Mar 18 '13 at 22:37

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I think it goes to 1/2 ... after all, you have half the series :-)

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What do you mean by "half the series"? – Chris Mar 18 '13 at 23:06