A048873 Number of non-isomorphic arrangements of n lines in the real projective plane such that the lines do not pass through a common point and no point belongs to more than 2 lines.

1, 1, 1, 4, 11

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• more

Comments

These are called simple arrangements.

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. 6.

Crossrefs

Cf. A003036, A048872.

Extensions

The next term is conjectured to be 135.