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A146890 a(n) is the maximal size of a set of lines in the complex n-dimensional space C^n with the property that all the subtriples of lines are pairwise congruent. 0
1, 4, 4, 8, 8, 12, 12, 16, 16 (list; graph; refs; listen; history; text; internal format)



a(n) is also the largest integer such that the (n-1)-dimensional complex projective space CP^(n-1) contains an F-regular subset of a(n) points (n>1).

a(n)=2n if and only if there exists a skew conference matrix of order 2n.


B. Et-Taoui, Sur les m-uples F-reguliers dans les espaces projectifs complexes, Geom. Dedicata, 63(1996), 297-308.

B. Et-Taoui, Equiangular lines in C^r, Indag. Mathem., N.S., 11(2000), 201-207.

B. Et-Taoui, Equiangular lines in C^r (part II), Indag. Mathem., N.S., 13(2002), 483-486.

Boumediene Et-Taoui, Complex Conference Matrices, Complex Hadamard Matrices and Complex Equiangular Tight Frames, in Convexity and Discrete Geometry Including Graph Theory, pp 181-191, Springer 2016; DOI:10.1007/978-3-319-28186-5_16


Table of n, a(n) for n=1..9.


a(10)=a(11)=20, a(12)=a(13)=24, a(14)=a(15)=28, a(16)=a(17)=32, a(18) and a(19) are between 32 and 36.


Sequence in context: A292135 A053249 A071339 * A168273 A278933 A351838

Adjacent sequences: A146887 A146888 A146889 * A146891 A146892 A146893




Boumediene Et-Taoui (boumediene.ettaoui(AT)uha.fr), Apr 16 2009



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Last modified December 10 02:09 EST 2022. Contains 358712 sequences. (Running on oeis4.)