proposition: Lemma symh_to_symm k : 'h_k = \sum_(l : 'P_k) 'm[l] :> SP.
proof: Proof. rewrite (homog_symmE (symh_homog n R k)); apply eq_bigr => l _. case: (leqP (size l) n) => [Hsz | /symm_oversize ->]; last by rewrite scaler0. by rewrite mcoeff_symh mdeg_mpart // sumn_intpartn eqxx scale1r. 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