1+$six, 1+$tri, 1+$tre,
                    $tri, $six,
                    $tre, $six,
                    ;;;
                $ratio[ $six ][ $tri ][ $tre ] = $$d_h[ $tri ][ $six ] / $$d_h[ $tre ][ $six ] ;
            }
        }
    }
    return \@ratio ;
}