proposition: Lemma expri2 i : (-1) ^+ i.+2 = (-1) ^+ i :> R.
proof: Proof. by rewrite !exprS !mulN1r opprK. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg ssrint fingroup perm) mathcomp(ssrcomplements freeg mpoly) sorted tools ordtype permuted partition skewpart composition Yamanouchi std tableau stdtab skewtab permcent antisym Schur_mpoly therule Schur_altdef unitriginv