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A370979 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 edges in H_n.

%I A370979 #12 Mar 26 2024 04:09:22
%S A370979 1,4,21,20,135,144,553,440,1575,1460,3729,3132,7527,6888,13605,12016,
%T A370979 23307,20988,36385,32420,54915,51216,79741,70776,113175,105300,154845,
%U A370979 144508,206799,195840,272893,255840,352275,335036,446845,422820,561031,534736,695877,659480,850463,815724
%N A370979 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 edges in H_n.
%C A370979 For the numbers of vertices and regions in G_n see A358746 and A370978.
%C A370979 H_n is the union of the graph G_n defined in A370976 and the polygon through the initial n points.
%F A370979 a(n) = A358783(n) if n even, a(n) = A358783(n) + n if n odd.
%F A370979 a(n) = A358783(n) + n if n even, a(n) = A358783(n) + 3*n if n odd.
%Y A370979 Cf. A358746, A358782, A358783, A370976, A370977, A370978.
%K A370979 nonn
%O A370979 1,2
%A A370979 _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 25 2024