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 A206712 Total number of distinct Hadamard matrices of order n. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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 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 August 11 12:12 EDT 2022. Contains 356065 sequences. (Running on oeis4.)