∀ a, m, b. 1 < #oc(a, x0) ∧ m < # x0 → a ∈ x0[m, b] ⊦ 1 < #oc(a, a0 + x0) ∧ m < #(a0 + x0) → a ∈ (a0 + x0)[m, b]
Used simplifier rules: oc-e: ⊦ #oc(a, []) = 0;%list freely generated by [], +;;