IMO 1992 LL KOR45

Let n be a positive integer. Prove that the number of ways

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IMO 1992 LL KOR45

Origin: KOR

Problem

Let n be a positive integer. Prove that the number of ways to express n as a sum of distinct positive integers (up to order) and the number of ways to express n as a sum of odd positive integers (up to order) are the same.