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 A018242 Number of projective order types; number of simple arrangements of n lines. 4
 1, 1, 1, 1, 1, 1, 4, 11, 135, 4381, 312114, 41693377 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,7 REFERENCES J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102. LINKS S. Felsner and J. E. Goodman, Pseudoline Arrangements. In: Toth, O'Rourke, Goodman (eds.) Handbook of Discrete and Computational Geometry, 3rd edn. CRC Press, 2018. Komei Fukuda, Hiroyuki Miyata, Sonoko Moriyama, Complete Enumeration of Small Realizable Oriented Matroids. Discrete Comput. Geom. 49 (2013), no. 2, 359-381. MR3017917. Also arXiv:1204.0645 [math.CO], 2012. - From N. J. A. Sloane, Feb 16 2013 FORMULA Asymptotics: a(n) = 2^(Theta(n log n)). This is Bachmann-Landau notation, that is, there are constants n_0, c, and d, such that for every n >= n_0 the inequality 2^(c n log n) <= a(n) <= 2^(d n log n) is satisfied. For more information see e.g. the Handbook of Discrete and Computational Geometry. - Manfred Scheucher, Sep 12 2019 CROSSREFS Cf. A006247, A006248, A063666. A diagonal of A222317. Sequence in context: A214113 A167418 A055979 * A006248 A119571 A089920 Adjacent sequences:  A018239 A018240 A018241 * A018243 A018244 A018245 KEYWORD nonn,more AUTHOR EXTENSIONS a(11) from Franz Aurenhammer (auren(AT)igi.tu-graz.ac.at), Feb 05 2002 STATUS approved

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Last modified January 17 18:14 EST 2020. Contains 330987 sequences. (Running on oeis4.)