 The orthogonality of rows implies that any two distinct rows have exactly "u"2 ± "u" positive entries in common.If "H" is interpreted as the incidence matrix of a block design, with 1 representing incidence and −1 representing non-incidence, then "H" corresponds to a symmetric 2-("v","k","λ") design with parameters (4"u"2, 2"u"2 ± "u", "u"2 ± "u").A design with these parameters is called a Menon design.