A368815 Number of edges in a regular 2n-gon when all vertices are connect by straight lines except for the n lines joining diametrically opposite vertices.

0, 4, 24, 104, 320, 648, 1540, 2832, 3996, 7860, 12100, 15552, 25376, 35084, 36840, 62752, 81600, 97272, 131556, 163720, 178332, 245564, 296516, 336960, 421600, 497172, 557280, 678552, 786016, 836520, 1038500, 1185344, 1301124, 1525444, 1720740, 1893600, 2166720, 2419612, 2628600, 2991440

Offset: 1

Author

Scott R. Shannon, Jan 06 2024

Keywords

• nonn

Comments

See A368813 and A368814 for images of the 2n-gons.

Crossrefs

Cf. A368813 (regions), A368814 (vertices), A368816 (k-gons), A368757, A135565.

Formula

a(n) = A368813(n) + A368814(n) - 1 by Euler's formula.