intros b
t : Th
Δ : Ctx
⊢ ∀ (b a : Lex (ℕ × ℕ)), a ≤ b → lindenbaumSequence t Δ a ⊆ lindenbaumSequence t Δ b
t : Th
Δ : Ctx
b : Lex (ℕ × ℕ)
⊢ ∀ (a : Lex (ℕ × ℕ)), a ≤ b → lindenbaumSequence t Δ a ⊆ lindenbaumSequence t Δ b