A392972 Number of finite regions in a complete bipartite graph where the n vertices of each part are placed on the vertices, and on opposite sides, of a regular 2n-gon.

0, 2, 12, 38, 100, 200, 412, 724, 1046, 1870, 2800, 3730, 5660, 7724, 8792, 13504, 17392, 21134, 27624, 34174, 38782, 50712, 60940, 70292, 85960, 101030, 114668, 137034, 158284, 173192, 208100, 237016, 262822, 303794, 342040, 378550, 429252, 478640, 523664

Offset

1,2

Links

Table of n, a(n) for n=1..39.

Scott R. Shannon, Image for n = 3.

Scott R. Shannon, Image for n = 6.

Scott R. Shannon, Image for n = 10.

Scott R. Shannon, Image for n = 15.

Scott R. Shannon, Image for n = 18.

Formula

a(n) = A392973(n) - A392971(n) + 1 by Euler's formula.

Crossrefs

Cf. A392971 (vertices), A392973 (edges), A290131, A007678, A392426, A359692.

Sequence in context: A305864 A324027 A035597 * A000913 A026575 A048349

Adjacent sequences: A392969 A392970 A392971 * A392973 A392974 A392975

Keyword

nonn

Author

Scott R. Shannon, Jan 29 2026

Status

approved