Glasnik Matematicki, Vol. 38, No.2 (2003), 201-210.

2-(56,12,3) DESIGNS AND THEIR CLASS GRAPHS

Sanja Rukavina

Department of Mathematics, Faculty of Philosophy, Omladinska 14, 51000 Rijeka, Croatia
e-mail: sanjar@mapef.pefri.hr


Abstract.   There exist exactly 1122 pairwise non-isomorphic 2-(56,12,3) designs being the residual designs of the known symmetric (71,15,3) designs. Six pairwise non-isomorphic strongly regular graphs with parameters (35,16,6,8) were constructed as class graphs of the obtained residual designs. Orders of the full automorphism groups of these graphs are 12, 32, 96, 192, 288 and 40320.

2000 Mathematics Subject Classification.   05B05, 05E30.

Key words and phrases.   Residual design, automorphism group, class graph.


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