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%I #14 Mar 27 2022 13:38:46
%S 1,2,3,6,4,2,2,2,2,2,2,12
%N a(n) is the number of Toeplitz anti-Hadamard matrices of order n whose sum of the inverse squares of their singular values is maximal.
%C Conjecture: a(1) = 1 and a(3) = 3 are the only odd terms.
%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.
%Y Cf. A351821.
%Y Cf. A005312, A005313, A351984, A352177.
%K nonn,hard,more
%O 1,2
%A _Stefano Spezia_, Mar 17 2022