22

Part of 1987 IMO Shortlist

Problems(1)

Old function problem (IMO SL 1987-P22)

Source:

Does there exist a function

f : \mathbb N \to \mathbb N

f(f(n)) =n + 1987

for every natural number

n

? (IMO Problem 4)
Proposed by Vietnam.

functionalgebrafunctional equationIMO ShortlistIMOIMO 1987