<p>There are <img alt="$2^{10} = 1024$" height="15" src="https://latex.artofproblemsolving.com/c/f/8/cf856775e3de1168a9a4f29bc68d3651d0bf6051.png" width="83" /> possible 10-letter strings in which each letter is either an A or a B. Find the number of such strings that do not have more than 3 adjacent letters that are identical.</p>

Question No: 391

There are $2^{10} = 1024$ possible 10-letter strings in which each letter is either an A or a B. Find the number of such strings that do not have more than 3 adjacent letters that are identical.

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Tags: Combinatorics

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