proposition: Lemma derivations_el B n s t : (s, t) el derivations B n -> M_enc_card s t ∈ M_enc_stack (derivations B n).
proof: Proof. Proof using M_ZF VIEQ. apply enc_stack_el. Qed.
imports: Undecidability.FOL.ZF Undecidability.FOL.Syntax.Facts Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Sets.ZF Lia Undecidability.PCP(PCP Util.PCP_facts Reductions.PCPb_iff_dPCPb) Undecidability(Shared.ListAutomation)