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Help with polygamma function

  1. Aug 13, 2009 #1
    So I've been working on a proof and Wolfram Alpha gives the following partial sum formula for one of the summations in the proof:

    http://www.wolframalpha.com/input/?i=sum[e^(-(2k+1)/x)/(1+e^(-(2k+1)/x)+)^2+]

    What does the terminology involving psi mean? I think it is the first derivative of the polygamma function, but I don't understand what the subscript e^(2/x) means.

    Thanks in advance for the help.
     
  2. jcsd
  3. Aug 14, 2009 #2

    CRGreathouse

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    I don't know what that subscript means either. It's funny that W|A thinks that it needs to tell you what the natural logarithm is but not the (variant of the) trigamma function.
     
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