New order 35 eight-Williamson

The following is a Hadamard matrix of order 8·35 = 280 constructed from a set of eight-Williamson matrices of order 35.  MathCheck found 78 inequivalent sets of such matrices in order 35 and this is especially interesting since regular Williamson matrices do not exist in order 35.  Prior to our work, searches had only been run up to order 29.  The coloured squares represent one and the white squares represent negative one and each eight-Williamson matrix is highlighted using a different colour.

A Hadamard matrix of order 280 constructed from eight-Williamson matrices