GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
#g2 f1 z1 c1 6x 6 0 0 -1 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 -1 -1 0 1 0 -1 0 0 -1 1 0 0 -1 0 0 0 -1 1 -1 6x 6 -1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 6x 6 3 -1 -1 1 1 0 -1 3 -1 -1 0 1 -1 -1 3 0 -1 -1 1 -1 0 3 -1 1 1 0 -1 -1 3 -1 0 1 -1 1 -1 3 6d0 % zentr -1 6d0 % cen -1 2^4 * 3^1 * 5 = 240 %order of the group