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A290865 a(n) = number of regions in the configuration A290447(n). 5
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

M. F. Hasler, Interactive web page for drawing the illustration for a(n).

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.

See also A290876.

Sequence in context: A147400 A002545 A153114 * 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 December 14 19:24 EST 2018. Contains 318106 sequences. (Running on oeis4.)