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Mock AIME 1 2006-2007 Problems/Problem 11

Revision as of 14:45, 24 July 2006 by Altheman (talk | contribs)
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11. Let $\mathcal{S}_{n}$ be the set of strings with only 0's or 1's with length $n$ such that any 3 adjacent place numbers sum to at least 1. For example, $00100$ works, but $10001$ does not. Find the number of elements in $\mathcal{S}_{11}$.

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