

A048872


Number of nonisomorphic arrangements of n lines in the real projective plane such that the lines do not all pass through a common point.


7




OFFSET

3,2


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

Table of n, a(n) for n=3..9.
Jacob E. Goodman, Joseph O'Rourke, and Csaba D. Tóth, editors, Handbook of Discrete and Computational Geometry, CRC Press, 2017, Table 5.6.1.
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 (simple arrangements), A063800 (arrangements of pseudolines).
Sequence in context: A009319 A009323 A247260 * A063800 A207137 A143674
Adjacent sequences: A048869 A048870 A048871 * A048873 A048874 A048875


KEYWORD

nonn,nice,more


AUTHOR

N. J. A. Sloane


EXTENSIONS

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


STATUS

approved



