proposition: Fact hfs_opair_pow r s t : r ∈ t -> s ∈ t -> hfs_opair r s ∈ iter hfs_pow t 2.
proof: Proof. intros; do 2 apply hfs_pair_pow; auto. Qed.
imports: List Arith Lia Max Wellfounded Setoid Eqdep_dec Bool Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list finite) Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.Shared.Libs.DLW.Wf(wf_finite wf_chains) Undecidability.FOL.TRAKHTENBROT(notations fol_ops membership btree)