simp [lh_prop_of_not_seq Hs, hn Hs]
case neg
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈𝚺₁
l s : M
h : Seq s → ∃ d ≤ 2 * s, d = domain s ∧ d = under l
hn : ¬Seq s → l = 0
Hs : ¬Seq s
⊢ l = lh s
no goals