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 A215897 #38 Jan 26 2019 11:09:24 %S A215897 1,0,1,2,3,4,8,18,27,44,267,1024,3645,6144,23859,50176,187377,531468, %T A215897 3302697,10616832,39337984,102546588,568833245,3073593600,8721488875, %U A215897 32998447572,164855413835,572108938470,2490252810073,10831449635712,68045615234375,282773291271138,1592413932070703,5234078743146888 %N A215897 a(n) = A215723(n) / 2^(n-1). %C A215897 A215723(n) is divisible by 2^(n-1), indeed the determinant of any n X n sign matrix is divisible by 2^(n-1). Proof: subtract the first row from other rows, the result is all rows except for the first are divisible by 2, hence by using expansion by minors proof follows. (Warren D. Smith on the math-fun mailing list, Aug 18 2012) %H A215897 Richard P. Brent, <a href="/A215897/b215897.txt">Table of n, a(n) for n = 1..52</a> %H A215897 Richard P. Brent and Adam B. Yedidia, <a href="http://arxiv.org/abs/1801.00399">Computation of maximal determinants of binary circulant matrices</a>, arXiv:1801.00399 [math.CO], 2018. %H A215897 R. P. Brent and A. Yedidia, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL21/Brent/brent11.html">Computation of maximal determinants of binary circulant matrices</a>, Journal of Integer Sequences, 21 (2018), article 18.5.6. %H A215897 <a href="/index/De#determinants">Index entries for sequences related to maximal determinants</a> %F A215897 a(n) = A215723(n) / 2^(n-1). %Y A215897 Cf. A215723 (Maximum determinant of an n X n circulant (1,-1)-matrix). %K A215897 nonn,hard %O A215897 1,4 %A A215897 _Joerg Arndt_, Aug 26 2012 %E A215897 a(23)-a(28) (as calculated by Warren Smith) from _W. Edwin Clark_, Sep 02 2012 %E A215897 a(29) onward from _Richard P. Brent_, Jan 02 2018