lemma pippo (f): f@❨𝟏❩⨮⇂f = f. * #p #f // qed. axiom pippo2 (f) (p): f@❨p❩ + (⇂*[ninj p]f)@❨𝟏❩ = f@❨↑p❩. lemma tr_uni_tl (n): (𝐢) = ⇂𝐮❨n❩. // qed. axiom tr_uni_tls_pos (p:pnat) (n): (𝐢) = ⇂*[p]𝐮❨n❩. (* #p #n >nsucc_pnpred