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 A290865 a(n) = number of regions in the configuration A290447(n). 9
 0, 1, 3, 7, 15, 30, 56, 98, 161, 250, 370, 536, 748, 1027, 1379, 1807, 2320, 2954, 3702, 4604, 5652, 6852, 8239, 9858, 11683, 13748, 16086, 18700, 21604, 24887, 28471, 32491, 36907, 41751, 47080, 52876, 59105, 65965, 73440, 81521, 90176 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS David Applegate, Table of n, a(n) for n = 1..100 N. J. A. Sloane (in collaboration with Scott R. Shannon), Art and Sequences, Slides of guest lecture in Math 640, Rutgers Univ., Feb 8, 2020. Mentions this sequence. EXAMPLE With 3 points, there are 3 semicircles above the baseline, which bound a(3) = 3 regions. With 4 points, there are 6 semicircles, defining 7 regions (use the Halser webpage with n = 3 and 4). - N. J. A. Sloane, Aug 12 2017 CROSSREFS Cf. A290447, A290866, A290867, A332723 (number of regions with k edges). See also A290876. Sequence in context: A002545 A153114 A325664 * A055795 A058695 A228447 Adjacent sequences:  A290862 A290863 A290864 * A290866 A290867 A290868 KEYWORD nonn AUTHOR David Applegate, Aug 12 2017 STATUS approved

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Last modified May 26 09:37 EDT 2020. Contains 334620 sequences. (Running on oeis4.)