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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
1, 2, 4, 17, 143, 4890, 460779 (list; graph; refs; listen; history; text; internal format)
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: A009323 A307125 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

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Last modified December 8 01:34 EST 2019. Contains 329850 sequences. (Running on oeis4.)