∀ {ι : Type u_1} {σ : Type u_2} {R : Type u_4} [inst : DecidableEq ι] [inst_1 : Semiring R] [inst_2 : SetLike σ R]
  [inst_3 : AddSubmonoidClass σ R] (A : ι → σ) [inst_4 : AddCommMonoid ι] [inst_5 : PartialOrder ι]
  [CanonicallyOrderedAdd ι] [inst_7 : SetLike.GradedMonoid A] [inst_8 : Sub ι] [OrderedSub ι] [AddLeftReflectLE ι]
  (r : DirectSum ι fun i => ↥(A i)) {i : ι} (r' : ↥(A i)) (n : ι) [inst_11 : Decidable (i ≤ n)],
  ↑((r * (DirectSum.of (fun i => ↥(A i)) i) r') n) = if i ≤ n then ↑(r (n - i)) * ↑r' else 0