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I am having a hard time summing the seemingly simple finite series:

$$1 - nx + n(n-1)x^2 - n(n-1)(n-2) x^3+\cdots+ (-1)^n n! x^n$$

Thanks for your help in advance!

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    It isn't quite clear what you're attempting to do, here. It's fine as it stands, so far as I can tell. Are you trying to factor it, or something?2012-06-27
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    The closed form for $$\sum_{k=0}^n k!\binom{n}{k}(-x)^k$$ involves the incomplete gamma function, which is nonelementary. Are you fine with that?2012-06-27
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    @J.M.: Isn't serie converges when $x=0$?2012-06-27
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    @Babak: I presume you missed the word *finite* in the question, then...2012-06-27
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    @J.M.: Yes, I am looking for the closed form if one exists. What is it in terms of the incomplete Gamma function? Thanks!2012-06-27

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