proposition: Lemma natnat_to_nat3_bij: bijective natnat_to_nat3.
proof: Proof. exists natnat_to_nat3_inv. apply: natnat_to_nat3_invK. apply: natnat_to_nat3K. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype order bigop ssralg) mathcomp(div ssrnum ssrint rat prime path binomial) mathcomp(tuple finset) gaia(fibm)