⊦ dups(x) ↔ (∃ a, x0, y, z. x = x0 + (a + (y + (a + z))))
∃ a, x0, y0, z. y = x0 + (a + (y0 + (a + z))), x ⊆m y, ∀ a. #oc(a, y) ≤ #oc(a, x) ⊦ dups(x)
Used terms: y