%N Number of non-isomorphic arrangements of n lines in the real projective plane such that the lines do not all pass through a common point.
%D J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102.
%D B. Grünbaum, Arrangements and Spreads. American Mathematical Society, Providence, RI, 1972, p. 4.
%H Jacob E. Goodman, Joseph O'Rourke, and Csaba D. Tóth, editors, <a href="https://www.csun.edu/~ctoth/Handbook/HDCG3.html">Handbook of Discrete and Computational Geometry</a>, CRC Press, 2017, Table 5.6.1.
%H N. J. A. Sloane, <a href="/A048872/a048872.pdf">Illustration of a(3) - a(6)</a> [based on Fig. 2.1 of Grünbaum, 1972]
%Y See A132346 for the sequence when we include the arrangement where the lines do pass through a common point, which is 1 greater than this.
%Y Cf. A003036, A048873, A090338, A090339, A241600, A250001, A018242 (simple arrangements), A063800 (arrangements of pseudolines).
%A _N. J. A. Sloane_
%E a(7)-a(9) from Handbook of Discrete and Computational Geometry, 2017, by _Andrey Zabolotskiy_, Oct 09 2017