A244020 Number of new points at the n-th step of the following iteration, starting with four points in general position in the real projective plane: dualize the current pointset to a family of lines, take all intersections of those lines, repeat.

4, 6, 3, 3, 6, 16, 84, 1716, 719628

Offset

1,1

Comments

A140468 is the main sequence for this problem. We have a(n) = b(n)-b(n-2), where b(n) = A140468(n).

Links

Table of n, a(n) for n=1..9.

Joshua Cooper, Mark Walters, Iterated point-line configurations grow doubly-exponentially, Discrete Comput. Geom. 43 (2010), no. 3, 554-562. MR2587837 (2011f:51016) 51M04 (52C35).

Shalosh B. Ekhad, Doron Zeilberger, Enumerative Geometrical Genealogy (Or: The Sex Life of Points and Lines), arXiv:1406.5157 [math.CO], (19-June-2014)

Crossrefs

Related sequences: A140468, A244020-A244026.

Sequence in context: A213080 A200365 A198121 * A179374 A081709 A200640

Adjacent sequences: A244017 A244018 A244019 * A244021 A244022 A244023

Keyword

nonn,more

Author

N. J. A. Sloane, Jun 20 2014

Status

approved