proposition: Lemma n2bin' n: n ^2 = U_nkbin n 0.
proof: Proof. rewrite n2bin -(mul1n (U_nkbin n 0)) - U_nkbin_pr addn0 //. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)