proposition: Lemma mulnf0 a n b: a != zero -> b < phi0 a -> (cons zero n zero) * b < phi0 a.
proof: Proof. case: b => // a' n' b'; rewrite phi0_lt1 /=. by case pa: (a'==zero); [case a | rewrite phi0_lt1]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)