A352478 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.

1, 2, 3, 6, 4, 2, 2, 2, 2, 2, 2, 12

Offset

1,2

Comments

Conjecture: a(1) = 1 and a(3) = 3 are the only odd terms.

Links

Table of n, a(n) for n=1..12.

R. L. Graham and N. J. A. Sloane, Anti-Hadamard matrices, Linear Alg. Applic., 62 (1984), 113-137.

Crossrefs

Cf. A351821.

Cf. A005312, A005313, A351984, A352177.

Sequence in context: A106834 A191658 A021427 * A091834 A050210 A003573

Adjacent sequences: A352475 A352476 A352477 * A352479 A352480 A352481

Keyword

nonn,hard,more

Author

Stefano Spezia, Mar 17 2022

Status

approved