∀ {R : Type u_1} [inst : CommMonoidWithZero R] [IsCancelMulZero R] [DecompositionMonoid R] {ι : Type u_2} {s : Finset ι}
  {f : ι → R}, (↑s).Pairwise (Function.onFun IsRelPrime f) → (∀ i ∈ s, Squarefree (f i)) → Squarefree (∏ i ∈ s, f i)