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Question Number 201839 by depressiveshrek last updated on 14/Dec/23
Commented by depressiveshrek last updated on 14/Dec/23
$${The}\:{last}\:{one}\:{means}: \\ $$$$\underset{{i}=\mathrm{0}} {\overset{{k}} {\sum}}{i}^{\mathrm{2}} \begin{pmatrix}{{k}}\\{{i}}\end{pmatrix}={k}\left({k}+\mathrm{1}\right)\mathrm{2}^{{k}−\mathrm{2}} \\ $$