[math-fun] max |determinant| for 38x38 circulant sign matrix

N=38 |det|=4.39152787578415089e+29 circ=-++-++---+---+-+--++----+-----++++-+-+ (For N=38 the computer says grle=-6002933426.61867619 whereas really the Graham-Lehmer number is exactly 0, which shows that a lot of roundoff error has crept in.)