Hadamard matrix
In mathematics a regular Hadamard matrix is a Hadamard matrix whose row and column sums are all equal. While the order of a Hadamard matrix must be 1, 2, or a multiple of 4, regular Hadamard matrices carry the further restriction that the order be a square number. The excess, denoted "E"("H"), of a Hadamard matrix "H" of order "n" is defined to be the sum of the entries of "H". The excess satisfies the bound