A352177 a(n) is the number of symmetric Toeplitz anti-Hadamard matrices of order n whose sum of the inverse squares of their singular values is maximal.

1, 2, 1, 2, 1, 3, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset

1,2

Links

Table of n, a(n) for n=1..19.

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

Formula

Conjectures: (Start)

a(n) = 1 for n > 9.

G.f.: x*(x + x^3 + 2*x^5 + x^8 + 1/(1 - x)). (End)

Crossrefs

Cf. A351240, A351241.

Cf. A005312, A005313, A351821, A351984.

Sequence in context: A074093 A324286 A265575 * A277367 A239936 A239701

Adjacent sequences: A352174 A352175 A352176 * A352178 A352179 A352180

Keyword

nonn,hard,more

Author

Stefano Spezia, Mar 08 2022

Status

approved