Sunday, 18 August 2013

Series k^2/k! with k=1 to infinity

Series k^2/k! with k=1 to infinity

A practice Math Subject GRE asked me to compute $\sum_{k=1}^\infty
\frac{k^2}{k!}$. The sum is equal to 2e, but I wasn't able to figure this
out using Maclarin series or discrete PDFs. What's the most elementary way
to solve this?

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