fact: Example Kostka_expl1 : Kostka_rec [:: 4; 3] [:: 3; 2; 2] == 2.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg ssrint fingroup perm) mathcomp(mpoly) tools combclass ordtype sorted partition tableau skewpart skewtab antisym Schur_mpoly freeSchur therule std stdtab unitriginv presentSn