∀ {α : Type u_1} (a : α) (t : List α) (motive : (s : List α) → (s = [] ∨ ∃ l ∈ t.inits, a :: l = s) → Prop) (s : List α)
  (o : s = [] ∨ ∃ l ∈ t.inits, a :: l = s),
  (∀ (a_1 : Unit), motive [] ⋯) → (∀ (s r : List α) (hr : r ∈ t.inits) (hs : a :: r = s), motive s ⋯) → motive s o