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 A217745 Number of regions in the exterior of a regular n-gon with all diagonals drawn. 3
 1, 4, 10, 18, 35, 64, 117, 190, 330, 492, 780, 1050, 1605, 2080, 2941 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,2 LINKS Table of n, a(n) for n=3..17. EXAMPLE a(3) = 1 since the equilateral triangle has no diagonals and therefore one exterior region (with infinite area). a(4) = 4 since the two diagonals of the square divide the exterior in four regions (with infinite area). a(5) = 10 since the ten diagonals of the regular pentagon divide the exterior in ten regions (with infinite area) of two different shapes. CROSSREFS Cf. A007678. Sequence in context: A050188 A062361 A038416 * A213949 A009913 A063591 Adjacent sequences: A217742 A217743 A217744 * A217746 A217747 A217748 KEYWORD nonn AUTHOR Martin Renner, Mar 23 2013 STATUS approved

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Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)