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A048872 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. 7

%I

%S 1,2,4,17,143,4890,460779

%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).

%K nonn,nice,more

%O 3,2

%A _N. J. A. Sloane_

%E a(7)-a(9) from Handbook of Discrete and Computational Geometry, 2017, by _Andrey Zabolotskiy_, Oct 09 2017

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Last modified January 22 14:04 EST 2020. Contains 331150 sequences. (Running on oeis4.)