Gallardo, Luis On a special case of a conjecture of Ryser about Hadamard circulant matrices. (English) Zbl 1321.15052 Appl. Math. E-Notes 12, 182-188 (2012). Summary: There is no Hadamard circulant matrices \(H\) of order \(n>4\) with (a) first column \([x_1,\dots,x_n]^\ast\) where \(x_1(x_i +x_{\frac{n}{2}+i})>2\) for all \(i=1,\dots,n/2\) and (b) 2 such that \(A+B\) is symmetric, where \(A,B\) are matrices of order \(n/2\) such that the first \(n/2\) lines of \(H\) have the form \([A,B]\). Cited in 5 Documents MSC: 15B34 Boolean and Hadamard matrices 11B30 Arithmetic combinatorics; higher degree uniformity PDFBibTeX XMLCite \textit{L. Gallardo}, Appl. Math. E-Notes 12, 182--188 (2012; Zbl 1321.15052) Full Text: EMIS