Dear Rudolf, a presentation that you can work with should have the subgroup U_6(2) visible, then you can enumerate cosets of it in Co_2 without much trouble. I don't know whether such an explicit presentation was ever published, but it is implicit in characterisations of Co_2 via a geometry called extended dual polar space, see e.g. A. A. Ivanov, Exceptional Extended Dual Polar Spaces, Eur. J. Comb. 18 (1997), 859-885, or Hans Cuypers, Extended near hexagons and line systems, Advances in Geometry 4 (2004), 181-214.
Hope this helps, Dmitrii _______________________________________________ Forum mailing list [email protected] http://mail.gap-system.org/mailman/listinfo/forum
