A1

Part of 1992 Putnam

Problems(1)

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

Source:

Find all functions

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

functionPutnamalgebra proposedalgebra