A290865 a(n) = number of regions in the configuration A290447(n).

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

Offset: 1

Author

David Applegate, Aug 12 2017

Keywords

• nonn

Examples

			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
		

Links

• David Applegate, Table of n, a(n) for n = 1..100
• M. F. Hasler, Interactive web page for drawing the illustration for a(n).
• 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.

Crossrefs

Cf. A290447, A290866, A290867, A332723 (number of regions with k edges).

See also A290876.