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A206712 Total number of distinct Hadamard matrices of order n. 1
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, 6326348471771854942942254850540801096975599808403992777086201935659972458534005637120000000000000, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is the total number of distinct Hadamard matrices of order n, ignoring all equivalences

REFERENCES

F. J. Aragon Artacho, J. M. Borwein, M. K. Tam, Douglas-Rachford Feasibility Methods for Matrix Completion Problems, 2013; http://www.carma.newcastle.edu.au/~jb616/DR_MatrixCompletion.pdf

LINKS

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

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

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Last modified July 12 21:31 EDT 2020. Contains 335669 sequences. (Running on oeis4.)