fact: Fixpoint is_skew_tableau inner t := if t is t0 :: t' then [&& head 0 inner + size t0 != 0, is_row t0, skew_dominate ((head 0 inner) - (head 0 (behead inner))) (head [::] t') t0 & is_skew_tableau (behead inner) t'] else inner == [::].
imports: HB(structures) mathcomp(all_ssreflect) tools partition skewpart Yamanouchi ordtype tableau std stdtab