6x8	% presentation for gorup in gp

 1  1  0  0  0  0  0  0
 2  2  2  0  0  0  0  0
 1  2 -1  2 -1  2  0  0
 1 -2  1 -2 -1 -2  0  0
 1  2  1 -2 -1  2 -1 -2
 1 -2  1  2 -1 -2 -1  2
