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%I #15 Jun 20 2014 13:28:42
%S 4,6,7,9,13,25,97,1741,719725
%N Number of points at the n-th step of the following iteration, starting with four points in general position in the real projective plane: dualize the current pointset to a family of lines, take all intersections of those lines, repeat.
%H K. Bezdek and J. Pach, <a href="http://dx.doi.org/10.5169/seals-38834">A point set everywhere dense in the plane</a>, Elem. Math. 40 (4) (1985) 81--84.
%H Joshua Cooper, Mark Walters, <a href="http://arxiv.org/abs/0807.1549">Iterated point-line configurations grow doubly-exponentially</a>, Discrete Comput. Geom. 43 (2010), no. 3, 554-562. MR2587837 (2011f:51016) 51M04 (52C35).
%H Shalosh B. Ekhad, Doron Zeilberger, <a href="http://arxiv.org/abs/1406.5157">Enumerative Geometrical Genealogy (Or: The Sex Life of Points and Lines)</a>, arXiv:1406.5157 [math.CO], (19-June-2014)
%H D. Ismailescu and R. Radoicic, <a href="http://dx.doi.org/10.1016/j.comgeo.2003.10.002">A dense planar point set from iterated line intersections</a> Comput. Geom. 27 (2004), no. 3, 257-267.
%e a(2)=6 because four points in general position define six lines.
%Y Related sequences: A244020-A244026.
%Y Bisections A243707, A243708.
%K hard,more,nonn
%O 1,1
%A Joshua Cooper (cooper(AT)math.sc.edu), Jun 28 2008
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