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.

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

Offset: 1

Author

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

Keywords

• nonn

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

• Wikipedia, Circular triangle.

Crossrefs

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