3,4

These are called simple arrangements.

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.

Table of n, a(n) for n=3..7.

Cf. A003036, A048872.

Sequence in context: A299880 A085649 A152396 * A091390 A321967 A230024

Adjacent sequences: A048870 A048871 A048872 * A048874 A048875 A048876

nonn,nice,more

N. J. A. Sloane

The next term is conjectured to be 135.

approved