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.

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

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• more

References

• J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102.
• B. Grünbaum, Arrangements and Spreads. American Mathematical Society, Providence, RI, 1972, p. 4.

Links

• Stefan Felsner and Jacob E. Goodman, Pseudoline Arrangements, Chapter 5 of Handbook of Discrete and Computational Geometry, CRC Press, 2017, see Table 5.6.1. [Specific reference for this sequence] - _N. J. A. Sloane_, Nov 14 2023
• Jacob E. Goodman, Joseph O'Rourke, and Csaba D. Tóth, editors, Handbook of Discrete and Computational Geometry, CRC Press, 2017, see Table 5.6.1. [General reference for 2017 edition of the Handbook]
• N. J. A. Sloane, Illustration of a(3) - a(6) [based on Fig. 2.1 of Grünbaum, 1972]

Crossrefs

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.

Cf. A003036, A048873, A090338, A090339, A241600, A250001, A018242, A063800 (arrangements of pseudolines).

Extensions

a(7)-a(9) from Handbook of Discrete and Computational Geometry, 2017, by Andrey Zabolotskiy, Oct 09 2017