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

Author

Stefano Spezia, Mar 17 2022

Keywords

• nonn
• hard
• more

Comments

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

Links

• 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.