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 A189976 #42 Sep 08 2022 08:45:56
%S A189976 1,1,5,5,15,15,35,35,70,70,126,126,210,210,330,330,495,495,715,715,
%T A189976 1001,1001,1365,1365,1820,1820,2380,2380,3060,3060,3876,3876,4845,
%U A189976 4845,5985,5985,7315,7315,8855,8855,10626
%N A189976 a(n) is the number of incongruent two-color bracelets of n beads, 8 of them black (A005514), having a diameter of symmetry.
%C A189976 For n >= 9, a(n-1) is the number of incongruent two-color bracelets of n beads, 9 from them are black (A032281), having a diameter of symmetry.
%H A189976 Vincenzo Librandi, <a href="/A189976/b189976.txt">Table of n, a(n) for n = 8..1000</a>
%H A189976 H. Gupta, <a href="https://web.archive.org/web/20151203100252/http://www.dli.gov.in/data_copy/upload/INSA/INSA_2/20005a66_964.pdf">Enumeration of incongruent cyclic k-gons</a>, Indian J. Pure and Appl. Math., 10 (1979), no.8, 964-999.
%H A189976 V. Shevelev, <a href="http://arxiv.org/abs/0710.1370">A problem of enumeration of two-color bracelets with several variations</a>, arXiv:0710.1370 [math.CO], 2007-2011.
%H A189976 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1,4,-4,-6,6,4,-4,-1,1).
%F A189976 a(n) = C(floor(n/2),4).
%F A189976 a(n+5) = A194005(n,n-4). [_Johannes W. Meijer_, Aug 15 2011]
%F A189976 G.f.: -x^8/((x-1)^5*(x+1)^4). [_Colin Barker_, Feb 06 2013]
%p A189976 A189976 :=proc(n): binomial(floor(n/2),4) end: seq(A189976(n), n=8..48); # _Johannes W. Meijer_, Aug 15 2011
%t A189976 Module[{c=Binomial[Range[4,30],4]},Riffle[c,c]] (* _Harvey P. Dale_, Aug 09 2014 *)
%t A189976 Table[(Binomial[Floor[n/2], 4]), {n, 8, 40}] (* _Vincenzo Librandi_, Aug 10 2014 *)
%o A189976 (Magma) [Binomial(Floor(n/2),4): n in[8..60]]; // _Vincenzo Librandi_, Aug 10 2014
%Y A189976 Cf. A005514, A032281, A008805, A058187.
%K A189976 nonn,easy
%O A189976 8,3
%A A189976 _Vladimir Shevelev_, May 03 2011
%E A189976 Data added and link corrected by _Johannes W. Meijer_, Aug 15 2011