This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A199006 #24 Jul 13 2025 19:55:16
%S A199006 192,21504,190080,10838016,16440,823616,74306
%N A199006 Related to number of Hadamard matrices of order 4n.
%C A199006 It seems that Álvarez et al. calculate these numbers by summing the orders of Aut(H) over inequivalent Hadamard matrices H. If so, a(8) = 20643963716 from Kharaghani and Tayfeh-Rezaie's Table 3. - _Andrei Zabolotskii_, Jul 08 2025
%H A199006 V. Álvarez, J. A. Armario, M. D. Frau, and F. Gudiel, <a href="https://doi.org/10.1016/j.laa.2011.05.018">The maximal determinant of cocyclic (-1, 1)-matrices over D_{2t}</a>, Linear Algebra and its Applications, 2011, Volume 436, Issue 4, 15 February 2012, Pages 858-873. See Table 2. The terms a(1)-a(7) are said to be computed from the data from N. J. A. Sloane's website.
%H A199006 Hadi Kharaghani and Behruz Tayfeh-Rezaie, <a href="https://doi.org/10.1002/jcd.21323">Hadamard Matrices of Order 32</a>, Journal of Combinatorial Designs, 21 (2013), 212-221; see also <a href="https://math.ipm.ac.ir/~tayfeh-r/papersandpreprints/H32typetwo.pdf">preprint</a>.
%H A199006 N. J. A. Sloane, <a href="http://neilsloane.com/hadamard/">A Library of Hadamard Matrices</a>.
%Y A199006 Cf. A007299, A048615, A048616, A199005, A199007, A206711.
%K A199006 nonn,hard,more
%O A199006 1,1
%A A199006 _N. J. A. Sloane_, Nov 01 2011