%I #10 Nov 12 2023 02:11:55
%S 1,8,88,444,1544,3584,8356,14996,26572,42144,69988,93264,148364,
%T 196120,261536,347544,483056,572832,783252,907472,1141668,1413512,
%U 1775972,1958684,2466452,2897004,3384128,3852068,4733632,5042324,6263264,6869784,7878988,9014840,10035784,10909592,13109608
%N Place n equally spaced points on each side of a square, and join each of these points by a chord to the 3*n new points on the other three sides: sequence gives number of regions in the resulting planar graph.
%C See A367276 for further information.
%H Scott R. Shannon, <a href="/A367278/a367278.png">Image for n = 1</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_1.png">Image for n = 2</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_2.png">Image for n = 3</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_3.png">Image for n = 4</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_4.png">Image for n = 5</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_5.png">Image for n = 9</a>.
%H Scott R. Shannon, <a href="/A367278/a367278_6.png">Image for n = 10</a>.
%F a(n) = A367279(n) - A367276(n) + 1 (Euler).
%Y Cf. A367276 (vertices), A367277 (interior vertices), A367279 (edges).
%K nonn
%O 0,2
%A _Scott R. Shannon_, Nov 11 2023