fact: Definition ax_HE3 := ∀ ∀ ∀ $2 ≡ $1 → $1 ≡ $0 → $2 ≡ $0.
imports: Lia Arith Undecidability.PCP.PCP Undecidability.PCP.Util.PCP_facts Undecidability.Synthetic.DecidabilityFacts Undecidability(FOL.Utils.FullSyntax) Undecidability(FOL.FSAT) Undecidability.Shared.ListAutomation