Definition codeArityLNTF (f : nat) :=
switchPR f
(switchPR (pred f)
(switchPR (pred (pred f)) (switchPR (pred (pred (pred f))) 0 1) 2) 3)
3.

Lemma codeArityLNTFIsCorrect2 :
forall n : nat,
codeArityLNTF n <> 0 -> exists f : Functions LNT, codeLNTFunction f = n.