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I have searched the internet for an exact answer and although I have found many decimal approximations, https://www.wolframalpha.com/input/?i=integrate+x%5E(-x)+from+0+to+infinity I have not been able to find an exact form.

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closed as off-topic by Andrés E. Caicedo, Alexandre Eremenko, Emil Jeřábek, Steven Landsburg, Nik Weaver Jun 12 at 14:16

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  • 1
    $\begingroup$ I doubt that there's a closed form. For $\int_0^1 x^{-x} \, dx$ there's the memorable formual $\sum_{n=1}^\infty n^{-n}$ [proof sketch: write $x^{-x} = \exp(-x\log x)$, use $e^t = \sum_{m=0}^\infty t^m/m!$, and integrate termwise]; but that's not really a closed form either. $\endgroup$ – Noam D. Elkies Jun 12 at 14:13

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