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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