A Search for Hadamard Matrices constructed from Williamson Matrices

We describe the implementation of a distributed computer search that uses Williamson's construction for Hadamard matrices. The search program is used to perform a complete search for matrices of orders 100 through 148. No new results are found, confirming existing results. We are convinced that no further matrices of any order less than 156 may be constructed. For reference purposes, we present tables of Hadamard matrices of orders 100 through 180 constructed using four circulant symmetric (1, -1) matrices in the Williamson array.