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Maximal sum of inverse squares of the singular values of symmetric anti-Hadamard matrices of order n.
(Formerly M2659)
7

%I M2659 #23 Feb 20 2022 22:46:04

%S 1,3,7,16,46,138,624

%N Maximal sum of inverse squares of the singular values of symmetric anti-Hadamard matrices of order n.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Noga Alon and Van H. Vu, <a href="https://doi.org/10.1006/jcta.1997.2780">Anti-Hadamard Matrices, Coin Weighing, Threshold Gates, and Indecomposable Hypergraphs</a>, Journal of Combinatorial Theory, Series A, Volume 79, Issue 1, July 1997, Pages 133-160.

%H R. L. Graham and N. J. A. Sloane, <a href="http://dx.doi.org/10.1016/0024-3795(84)90090-9">Anti-Hadamard matrices</a>, Linear Alg. Applic., 62 (1984), 113-137, Table 1.

%Y Cf. A005313.

%K nonn,hard,more

%O 1,2

%A _N. J. A. Sloane_.

%E Definition corrected by _Stefano Spezia_, Jan 30 2022

%E a(7) confirmed and inserted by _Stefano Spezia_, Feb 20 2022