We examine the codewords with best possible merit factor (minimum sum of squares of periodic autocorrelations) for a variety of lengths. Many different approaches were tried in an attempt to find construction methods for such codewords, or for codewords with good but non-optimal merit factors.
Michael W. Cammarano and Anthony G. Kirilusha. An Examination of Codewords with Optimal Merit Factor. Technical paper (TR-99-02). Math and Computer Science Technical Report Series. Richmond, Virginia: Department of Mathematics and Computer Science, University of Richmond, April, 1999.