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A002853
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Maximal size of a set of equiangular lines in n dimensions.
(Formerly M2514 N0994)
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1
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1, 3, 6, 6, 10, 16, 28, 28, 28, 28, 28, 28, 28, 28, 36, 40, 48
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OFFSET
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1,2
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COMMENTS
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The sequence continues: 57 <= a(18) <= 60, 72 <= a(19) <= 74, 90 <= a(20) <= 94, a(21) = 126, a(22) = 176, a(23) = ... = a(41) = 276, 276 <= a(42) <= 288, a(43) = 344.
Seidel (1995) claimed, without proof, that a(14) = 28. This was not known at the time. See Greaves, Koolen, Munemasa, Szollosi, (2016). - Ferenc Szollosi, Aug 31 2015
a(14) is now known to be 28 (see Greaves et al. (2020)). - N. J. A. Sloane, Feb 21 2020
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REFERENCES
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W. W. R. Ball and H. S. M. Coxeter, "Mathematical Recreations and Essays," 13th Ed. Dover, p. 307.
F. Buekenhout, ed., Handbook of Incidence Geometry, 1995, p. 884.
Greaves, G., Koolen, J. H., Munemasa, A., & Szöllősi, F. (2016). Equiangular lines in Euclidean spaces. Journal of Combinatorial Theory, Series A, 138, 208-235.
Lin, Yen-Chi Roger, and Wei-Hsuan Yu. "Equiangular lines and the Lemmens-Seidel conjecture." Discrete Mathematics 343.2 (2020): 111667.
Lin, Yen-Chi Roger, and Wei-Hsuan Yu. "Saturated configuration and new large construction of equiangular lines", Linear Algebra Appl., 588, 272-281, 2020.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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P. W. H. Lemmens and J. J. Seidel, Equiangular lines, J. Algebra, 24 (1973), 494-512.
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CROSSREFS
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KEYWORD
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nonn,nice,hard,more
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AUTHOR
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EXTENSIONS
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Updates to a(14), a(15), a(16), a(19), a(20) added from Greaves et al. (2020) by N. J. A. Sloane, Feb 21 2020. Thanks to Yen-Chi Roger Lin for telling us about this paper.
Updates to a(17) and a(18) added from Greaves et al. (2021) by Gary R. W. Greaves, Jul 10 2021
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STATUS
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approved
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