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 A358783 The number of edges formed when every pair of n points, placed at the vertices of a regular n-gon, are connected by a circle and where the points lie at the ends of the circle's diameter. 13
 2, 12, 16, 120, 138, 532, 432, 1548, 1450, 3696, 3120, 7488, 6874, 13560, 12000, 23256, 20970, 36328, 32400, 54852, 51194, 79672, 70752, 113100, 105274, 154764, 144480, 206712, 195810, 272800, 255808, 352176, 335002, 446740, 422784, 560920, 534698, 695760, 659440, 850340, 815682 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Conjecture: for odd values of n all vertices are simple, other than those defining the diameters of the circles. No formula for n, or only the odd values of n, is currently known. See A358746 and A358782 for images of the circles. The author thanks Zach Shannon some of whose code was used in the generation of this sequence. If n is odd, the circle containing the initial n points is not part of the graph (compare A370976-A370979). - N. J. A. Sloane, Mar 25 2024 LINKS Table of n, a(n) for n=2..42. FORMULA a(n) = A358746(n) + A358782(n) - 1 by Euler's formula. CROSSREFS Cf. A358746 (vertices), A358782 (regions), A359009 (k-gons), A135565, A344899. See allso A370976-A370979. Sequence in context: A274890 A327570 A057123 * A134833 A057827 A266802 Adjacent sequences: A358780 A358781 A358782 * A358784 A358785 A358786 KEYWORD nonn AUTHOR Scott R. Shannon, Nov 30 2022 STATUS approved

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Last modified August 2 19:53 EDT 2024. Contains 374875 sequences. (Running on oeis4.)