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A340687 The number of edges on a concave circular triangle formed by the straight line segments mutually connecting all vertices and all points that divide the sides into n equal parts. 4
3, 21, 51, 177, 354, 852, 1686, 3036, 5994, 8550, 12933, 16938, 24303, 30192, 41616, 52581, 66600, 82857, 101199, 128409, 153669, 194505, 227193, 271635, 320898, 368703, 431640, 490884, 578805, 646869, 744717, 851214, 943068, 1071741, 1195638, 1367913, 1523694, 1713300, 1885389, 2082696 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The terms are from numeric computation - no formula for a(n) is currently known.

See A340685 for images of the regions and A340686 for images of the vertices.

LINKS

Table of n, a(n) for n=1..40.

Wikipedia, Circular triangle.

CROSSREFS

Cf. A340685 (regions), A340686 (vertices), A340688 (n-gons), A340613, A007678, A092867.

Sequence in context: A219069 A027499 A303834 * A152773 A039595 A033567

Adjacent sequences:  A340684 A340685 A340686 * A340688 A340689 A340690

KEYWORD

nonn

AUTHOR

Scott R. Shannon and N. J. A. Sloane, Jan 16 2021

STATUS

approved

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Last modified April 11 04:03 EDT 2021. Contains 342886 sequences. (Running on oeis4.)