A244020 - OEIS

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

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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