Abstract Let A be a subset of an additive abelian semigroup S and let hA be the h -fold sumset of A. The following question is considered. Let (Aq) ₐ=₁^ be a strictly decreasing sequence of sets in S and let A = ₐ=₁^ Aq. When does one have align* hA = ₐ=₁^ hAq align* for some or all h 2?
Melvyn B. Nathanson (Thu,) studied this question.