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MathNet 2011 Question 85

Math Olympiad Vault · MathNet 2011

Question 85

Consider all the subsets of $\{1, 2, \ldots, N\}$ that do not contain two consecutive numbers. For each subset, calculate the product of the members of the set. What is the sum of the squares of these products?

Note: the product of the elements of an empty set is one.