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 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). 0
 1, 1, 2, 10, 36 (list; graph; refs; listen; history; text; internal format)
 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 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

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Last modified September 27 19:34 EDT 2021. Contains 347694 sequences. (Running on oeis4.)