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 A350547 Maximum size of a set of points taken from a hexagonal section of a hexagonal grid with side length n such that no three selected points form an equilateral triangle. 0
 1, 4, 9, 15, 22, 28, 36 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The hexagon with side length n has n+1 points along each edge and contains a total of A003215(n) points. The following lower bounds are known: a(7) >= 44; a(8) >= 52; a(9) >= 60. All currently known values and lower bounds can be achieved by a configuration with reflective symmetry. LINKS Table of n, a(n) for n=0..6. EXAMPLE For n = 4 the a(4) = 22 solution, unique up to rotation, is: . o x x o x x x o o o x x o o o o x o o o o o o o x x x o o o o o o o x x x o o o o o o o x o o o o x x o o o x x x o x x o . CROSSREFS Cf. A003215, A008893, A240114. Sequence in context: A066495 A313298 A313299 * A055999 A134227 A022945 Adjacent sequences: A350544 A350545 A350546 * A350548 A350549 A350550 KEYWORD nonn,hard,more AUTHOR Zachary DeStefano, Jan 06 2022 STATUS approved

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Last modified December 11 13:02 EST 2023. Contains 367727 sequences. (Running on oeis4.)