fact: Definition skew_def phK n : 'M[K]_(n * n) := (\sum_(i | ((i.2 : 'I__) < (i.1 : 'I__))%N) <<skew_vec i.1 i.2>>)%MS.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg ssrint div ssrnum rat poly closed_field) mathcomp(polyrcf matrix mxalgebra tuple mxpoly zmodp binomial realalg) mathcomp(mxpoly)