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 A060206 #28 Sep 03 2019 09:56:36 %S A060206 1,2,10,66,504,4210,37378,346846,3328188,32786630,329903058, %T A060206 3377919260,35095839848,369192702554,3925446804750,42126805350798, %U A060206 455792943581400,4967158911871358,54480174340453578,600994488311709056,6664356253639465480 %N A060206 Number of rotationally symmetric closed meanders of length 4n+2. %C A060206 Closed meanders of other lengths do not have rotational symmetry. - _Andrew Howroyd_, Nov 24 2015 %C A060206 See A077460 for additional information on the symmetries of closed meanders. %H A060206 R. Bacher, <a href="http://www-fourier.ujf-grenoble.fr/sites/default/files/ref_478.pdf">Meander algebras</a> %H A060206 Andrew Howroyd, <a href="/A060206/a060206.pdf">Illustration of a(1) and a(2)</a> %F A060206 a(n) = A000682(2n + 1). - _Andrew Howroyd_, Nov 24 2015 %t A060206 A000682 = Import["https://oeis.org/A000682/b000682.txt", "Table"][[All, 2]]; %t A060206 a[n_] := A000682[[2n + 1]]; %t A060206 a /@ Range[0, 20] (* _Jean-François Alcover_, Sep 03 2019 *) %Y A060206 Cf. A000682, A005315, A077055, A077460, A223096. %Y A060206 Meander sequences in Bacher's paper: A060066, A060089, A060111, A060148, A060149, A060174, A060198. %K A060206 nonn,nice %O A060206 0,2 %A A060206 _N. J. A. Sloane_, Apr 10 2001 %E A060206 Name edited by _Andrew Howroyd_, Nov 24 2015 %E A060206 a(7)-a(20) from _Andrew Howroyd_, Nov 24 2015