IMO 1985 LL AUS3

A function f has the following property: If k > 1, j > 1,

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IMO 1985 LL AUS3

Origin: AUS

Problem

A function f has the following property: If k > 1, j > 1, and (k, j) = m, then f(kj) = f(m) (f(k/m) + f(j/m)). What values can f(1984) and f(1985) take?