(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Does anyone know a clever way to prove that

[tex] \sum_{i=1}^{n}i^2 {n \choose i} = n(n+1) 2^{n-2} [/tex]

where B(n,i) is n take i?

I can do it, but I had to divide into the cases of n = odd and n = even and it took about 1 page front and back. I'm sure there is a trick.

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Summation proof

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