MATLAB function producing Alan Edelman's matrix for which det is computed as the wrong integer.

edelman.m

function A = edelman
%EDELMAN  Alan Edelman's matrix for which det is computed as the wrong integer.
%   A = EDELMAN is a 27-by-27 matrix of 1s and -1s for which the
%   MATLAB det function returns an odd integer, though the exact
%   determinant is an even integer.

A = [%
 1  1  1  1 -1 -1 -1  1  1 -1  1 -1 -1  1 -1  1 -1  1 -1 -1 -1 -1 -1  1 -1 -1 -1
 1 -1 -1  1 -1  1 -1 -1 -1 -1 -1  1 -1 -1 -1 -1 -1  1 -1 -1 -1 -1  1 -1  1  1  1
-1  1 -1 -1  1  1  1  1  1 -1  1 -1  1  1  1  1 -1 -1  1 -1 -1  1  1 -1  1  1 -1
-1 -1  1 -1 -1 -1 -1  1 -1 -1 -1 -1  1 -1  1 -1 -1  1  1 -1 -1  1 -1 -1 -1 -1 -1
-1  1  1 -1 -1 -1 -1 -1  1 -1 -1  1  1  1 -1 -1 -1 -1 -1  1  1  1 -1  1  1  1 -1
 1  1  1  1  1  1 -1  1 -1 -1  1  1 -1  1 -1 -1  1  1 -1 -1  1  1  1  1 -1  1 -1
-1 -1 -1 -1 -1 -1  1 -1  1 -1  1 -1  1 -1  1  1  1  1  1 -1  1 -1  1 -1 -1  1 -1
 1  1  1 -1  1  1 -1 -1  1  1 -1 -1  1  1 -1  1 -1  1  1  1  1  1 -1 -1  1  1 -1
-1  1 -1  1  1  1 -1 -1  1 -1  1  1  1  1 -1  1  1  1 -1  1  1 -1  1  1  1 -1 -1
-1  1 -1  1  1 -1 -1 -1 -1  1  1  1  1  1 -1  1 -1  1  1 -1 -1  1  1  1  1 -1 -1
-1 -1 -1 -1  1  1 -1 -1 -1  1  1 -1 -1  1 -1 -1  1  1  1  1 -1  1  1  1 -1 -1  1
 1  1 -1 -1  1 -1 -1 -1  1 -1 -1 -1 -1 -1 -1  1 -1  1 -1  1  1 -1  1  1  1 -1 -1
-1  1 -1 -1 -1 -1  1 -1 -1 -1 -1  1 -1 -1  1  1 -1  1 -1 -1  1  1 -1 -1  1 -1 -1
 1  1 -1  1  1 -1  1  1 -1 -1 -1  1  1  1  1 -1 -1  1 -1  1  1 -1  1 -1 -1  1 -1
-1  1 -1  1 -1  1  1  1 -1 -1  1  1 -1 -1 -1 -1 -1  1  1  1  1  1 -1  1  1 -1 -1
-1 -1  1 -1  1 -1  1 -1 -1  1 -1 -1 -1 -1 -1 -1  1 -1  1 -1  1  1 -1  1 -1 -1  1
 1  1 -1  1  1 -1  1 -1 -1  1  1 -1 -1  1 -1 -1  1  1 -1  1 -1  1  1 -1  1  1 -1
 1  1 -1  1  1 -1  1  1  1 -1  1 -1  1 -1  1  1  1  1 -1 -1 -1  1  1  1 -1  1  1
 1 -1 -1 -1  1 -1  1 -1 -1 -1 -1  1  1 -1 -1  1  1 -1 -1 -1  1 -1  1  1  1  1 -1
-1 -1 -1  1  1 -1  1 -1  1 -1  1  1  1  1  1 -1 -1 -1 -1 -1 -1  1  1  1 -1 -1 -1
 1  1 -1 -1 -1 -1 -1 -1 -1 -1  1  1  1 -1 -1  1 -1 -1  1 -1 -1  1  1 -1 -1 -1  1
-1 -1  1  1 -1 -1  1 -1 -1 -1  1 -1  1 -1 -1  1  1 -1  1 -1  1  1 -1  1 -1  1 -1
-1  1 -1  1  1  1  1  1 -1  1 -1  1 -1  1 -1  1  1  1  1  1  1  1  1 -1 -1 -1  1
-1 -1  1  1  1 -1 -1 -1  1 -1  1 -1 -1  1 -1 -1 -1 -1  1 -1 -1  1  1  1  1  1 -1
 1  1  1  1  1 -1  1 -1  1 -1 -1  1  1 -1 -1  1  1  1 -1  1 -1 -1  1  1 -1  1  1
 1 -1  1 -1  1 -1  1  1 -1  1 -1  1  1 -1  1 -1 -1  1 -1 -1  1  1  1 -1  1 -1 -1
 1 -1  1  1 -1 -1  1  1  1 -1  1  1 -1  1  1  1  1  1 -1  1 -1  1 -1  1  1 -1  1];

It's been awhile since Alan's name has been associated with MATLAB code ;-)