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f ( f (n)) = f ( f (n+2)+2) = n

Source:

February 15, 2008
functionPutnamalgebra proposedalgebra

Problem Statement

Find all functions f:Zā†’Z f : Z\rightarrow Z for which we have f (0) \equal{} 1 and f ( f (n)) \equal{} f ( f (n\plus{}2)\plus{}2) \equal{} n, for every natural number n n.
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