proposition: Lemma sumn_conj_part sh : sumn (conj_part sh) = sumn sh.
proof: Proof. by elim: sh => //= s0 s IHs; rewrite sumn_incr_first_n IHs addnC. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype