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MathNet 2011 Question 14

Math Olympiad Vault · MathNet 2011

Question 14

Each square in a $3 \times 10$ grid is colored black or white. Let $N$ be the number of ways this can be done in such a way that no five squares in an 'X' configuration (as shown by the black squares below) are all white or all black. Determine $\sqrt{N}$.

Question illustration