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%I #25 Sep 07 2021 02:46:08
%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,4,14,162,4713,157211
%N Number of triangle-free configurations of type (n_3).
%H A. Alazemi and A. Betten, <a href="https://doi.org/10.1155/2010/767361">Classification of Triangle-Free 22_3 Configurations</a>, International Journal of Combinatorics, Volume 2010, Article ID 767361.
%H A. Betten, G. Brinkmann and T. Pisanski, <a href="https://doi.org/10.1016/S0166-218X(99)00143-2">Counting symmetric configurations v_3</a>, Discrete Appl. Math., 99 (2000), 331-338.
%H M. Boben et al., <a href="https://doi.org/10.1007/s00454-005-1224-9">Small triangle-free configurations of points and lines</a>, Discrete Comput. Geom., 35 (2006), 405-427.
%Y Cf. A001403.
%K nonn,more,hard
%O 1,18
%A _N. J. A. Sloane_
%E a(22) from _Abdullah Alazemi_, Sep 05 2021