A206712 Total number of distinct Hadamard matrices of order n.

2, 8, 0, 768, 0, 0, 0, 4954521600, 0, 0, 0, 20251509535014912000, 0, 0, 0, 88526812916367202104587059200000, 0, 0, 0, 3776127947893930552689423154306445475840000000, 0, 0, 0, 92624181047745713568610317051197596401168530978226831360000000, 0, 0, 0, 886156947284057553944669848348035536068124589065755283423684984832000000000000, 0, 0, 0

Offset

1,1

Comments

a(n) is the total number of distinct Hadamard matrices of order n, ignoring all equivalences.

Links

Brendan McKay, Table of n, a(n) for n = 1..35

F. J. Aragon Artacho, J. M. Borwein, M. K. Tam, Douglas-Rachford Feasibility Methods for Matrix Completion Problems, March 2014.

H. Kharaghani and B. Tayfeh-Rezaie, Hadamard matrices of order 32

Index entries for sequences related to Hadamard matrices

Formula

a(4n) = A206711(n) = A048615(n)/A048616(n) * (2^n * n!)^2.

For n>1, a(4n+1) = a(4n+2) = a(4n+3) = 0.

Crossrefs

Cf. A007299, A036297, A206711.

Sequence in context: A288873 A160636 A282626 * A293777 A200704 A257955

Adjacent sequences: A206709 A206710 A206711 * A206713 A206714 A206715

Keyword

nonn,nice

Author

Brendan McKay, Feb 11 2012 (entered by N. J. A. Sloane)

Status

approved