proposition: Lemma fsub_cons_rec0 x0 t n (ts : terms n) x : x = x0+2 -> fsub x0 (Vcons t ts) x = fsub (x0+1) ts x.
proof: Proof. intro. eapply fsub_cons_rec with (k := 0). lia. Qed.
imports: CoLoR(AInterpretation AContext VecUtil NatUtil LogicUtil ListUtil EqUtil)