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Calculate the sum for every natural n - ILL 1990 ISR2

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September 18, 2010
algebra proposedalgebra

Problem Statement

Let nn be an arbitrary positive integer. Calculate Sn=∑r=0n2r−2n(2n−rn).S_n = \sum_{r=0}^n 2^{r-2n} \binom{2n-r}{n}.
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