Remark codeTermFreeVar :
 forall s : fol.Term L, fold_right max 0 (freeVarTerm L s) <= codeTerm s.Remark maxVarFreeVar :
 forall f : fol.Formula L,
 fold_right max 0 (freeVarFormula L f) <= fold_right max 0 (varFormula f).Remark maxSubTerm :
 forall (t : fol.Term L) (v : nat) (s : fol.Term L),
 fold_right max 0 (freeVarTerm L (substituteTerm L t v s)) <=
 fold_right max 0 (freeVarTerm L s ++ freeVarTerm L t).Remark maxSubTerms :
 forall (n : nat) (ts : fol.Terms L n) (v : nat) (s : fol.Term L),
 fold_right max 0 (freeVarTerms L n (substituteTerms L n ts v s)) <=
 fold_right max 0 (freeVarTerm L s ++ freeVarTerms L n ts).Definition pow3 : nat -> nat :=
  nat_rec (fun _ => nat) 1 (fun _ rec : nat => rec + (rec + rec)).

Lemma pow3IsPR : isPR 1 pow3.