A191101 Number of regions in a complete but borderless regular polygon.

6, 18, 43, 72, 145, 210, 364, 432, 768, 938, 1441, 1680, 2483, 2448, 4010, 4480, 6154, 6798, 9063, 9000, 12901, 13962, 17848, 19152, 24100, 21450, 31869, 33824, 41383, 43758, 52886, 52920, 66638, 69958, 82915, 86760, 102009

Offset: 5

Author

Stefan Hannie, May 25 2011

Keywords

• nonn
• easy

Comments

A complete borderless polygon is one where each vertex is connected to every other vertex except for adjacent vertices. Adjacent vertices are not connected by edges. The result is a polygon interior.

Crossrefs

Cf. A007678.

Formula

a(n) = A007678(n) - n.

Extensions

a(8) onward corrected by T. D. Noe, Jun 02 2011