This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A018242 #57 Apr 16 2025 14:20:23 %S A018242 1,1,1,1,1,1,4,11,135,4381,312114,41693377 %N A018242 Number of projective order types. %C A018242 Table 5.6.1 in the Felsner-Goodman survey contains this sequence in the second row, but the line is incorrectly labeled. The origin of these data is the paper of Aichholzer and Krasser. - _Günter Rote_, Apr 16 2025 %H A018242 Oswin Aichholzer, Hannes Krasser: <a href="https://doi.org/10.1016%2Fj.comgeo.2005.07.005">Abstract order type extension and new results on the rectilinear crossing number</a>. Comput. Geom. 36(1), 2-15 (2007), Table 1 %H A018242 Stefan Felsner and Jacob E. Goodman, <a href="https://www.csun.edu/~ctoth/Handbook/chap5.pdf">Pseudoline Arrangements</a>, Chapter 5 of <a href="https://www.csun.edu/~ctoth/Handbook/HDCG3.html">Handbook of Discrete and Computational Geometry</a>, 3rd edition, Jacob E. Goodman, Joseph O'Rourke, and Csaba D. Tóth, editors, CRC Press, 2017, see Table 5.6.1. [<a href="https://doi.org/10.1201/9781315119601">alternative link</a>][<a href="https://page.math.tu-berlin.de/~felsner/Paper/pseudol.pdf">alternative link</a>] [Specific reference for this sequence] - N. J. A. Sloane, Nov 14 2023 %H A018242 Komei Fukuda, Hiroyuki Miyata, Sonoko Moriyama, <a href="https://doi.org/10.1007/s00454-012-9470-0">Complete Enumeration of Small Realizable Oriented Matroids</a>. Discrete Comput. Geom. 49 (2013), no. 2, 359-381, see Table 2. MR3017917. Also arXiv:<a href="http://arxiv.org/abs/1204.0645">1204.0645</a> [math.CO], 2012. - From _N. J. A. Sloane_, Feb 16 2013 %F A018242 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 %Y A018242 Cf. A006247, A006248, A063666. A diagonal of A222317. %K A018242 nonn,hard,more %O A018242 0,7 %A A018242 _N. J. A. Sloane_ %E A018242 a(11) from Franz Aurenhammer (auren(AT)igi.tu-graz.ac.at), Feb 05 2002