I am unsure of how Wolfram Alpha computes the following partial sum: sum of (n-k)!/(n-r-k)! from 1 to n-r - Wolfram|Alpha If someone could explain to me how the equation for the partial sum is derived I'd greatly appreciate it. Thanks!
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Originally Posted by cyclic1001 I am unsure of how Wolfram Alpha computes the following partial sum: sum of (n-k)!/(n-r-k)! from 1 to n-r - Wolfram|Alpha If someone could explain to me how the equation for the partial sum is derived I'd greatly appreciate it. Thanks! First, simplify... , so . Therefore . Can you now try to work out ?
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