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A370978 Draw a regular n-gon and the enclosing circle, then for each pair of vertices X, Y, draw a circle with diameter XY; the union of these figures is the graph H_n; sequence gives number of regions in H_n.

%I A370978 #30 Mar 26 2024 07:30:59
%S A370978 1,3,16,16,81,91,302,272,829,831,1926,1752,3849,3739,6916,6464,11799,
%T A370978 11143,18374,17180,27679,26819,40136,37200,56901,54679,77788,74816,
%U A370978 103821,101071,136928,131776,176683,172143,224036,216936,281201,273867,348700,337520,426073,416683
%N A370978 Draw a regular n-gon and the enclosing circle, then for each pair of vertices X, Y, draw a circle with diameter XY; the union of these figures is the graph H_n; sequence gives number of regions in H_n.
%C A370978 H_n is the union of the graph G_n defined in A370976 and the polygon through the initial n points.
%H A370978 Scott R. Shannon, <a href="/A370978/a370978.gif">Image for n = 3</a>.
%H A370978 Scott R. Shannon, <a href="/A370978/a370978_1.gif">Image for n = 5</a>.
%F A370978 a(n) = A358782(n) + n if n even, a(n) = A358782(n) + 3*n if n odd.
%Y A370978 Cf. A358746, A358782, A358783, A370976, A370977, A370979.
%K A370978 nonn
%O A370978 1,2
%A A370978 _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 25 2024