A309889 a(n) is the maximal number of regions in the Euclidean plane made by superimposing a simple n-gon onto the resulting plane figure of a(n-1).

1, 1, 2, 10, 36

Offset

1,3

Comments

There is initially one region and the 1-gon and 2-gon are ignored, so a(1) and a(2) result in one region. Each line of the n-gon should cross as many lines as possible and avoid intersecting previous intersections.

Links

Table of n, a(n) for n=1..5.

Example

For n = 3 the plane is empty, so the trigon can only create 1 extra region. Thus a(3) = 2.
For n = 4 each tetragon edge intersects a maximum of 2 trigon edges, creating a total of 4 new regions. Two trigon edges intersect 2 tetragon edges, adding 4 regions, and the last trigon edge intersects all 4 tetragon edges, adding another 4 regions. Thus a(4) = 2 + 4 + 4 = 10.

Crossrefs

Cf. A000124.

Sequence in context: A327075 A135963 A140954 * A155894 A317454 A244715

Adjacent sequences: A309886 A309887 A309888 * A309890 A309891 A309892

Keyword

nonn,more

Author

Arran Ireland, Aug 21 2019

Status

approved