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Question about sum of integer involving factorial notation

  1. Jan 1, 2005 #1
    I have my question and my problem in the attachment that followed.

    Attached Files:

  2. jcsd
  3. Jan 1, 2005 #2


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    Damn right you don't know how to continue. That is because you took r out of the sumation sign and you cannot do that because r is the thing that varies in your sumationg sign. r is nothing without the sumation sign!

    The proof is easily done by induction.
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