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 A006657 M2037 #32 Jun 17 2022 12:24:48 %S A006657 2,12,84,640,5236,45164,406012,3772008,35994184,351173328,3490681428, %T A006657 35253449296,360946635312,3739935635756,39159200588780, %U A006657 413836299216608,4409705753032648,47337525317450816,511563350415103008 %N A006657 Number of closed meanders with 2 components and 2n bridges. %D A006657 S. K. Lando and A. K. Zvonkin "Plane and projective meanders", Séries Formelles et Combinatoire Algébrique. Laboratoire Bordelais de Recherche Informatique, Université Bordeaux I, 1991, pp. 287-303. %D A006657 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006657 P. Di Francesco, O. Golinelli and E. Guitter, <a href="http://arXiv.org/abs/hep-th/9506030">Meander, folding and arch statistics</a>, arXiv:hep-th/9506030, 1995. %H A006657 S. K. Lando and A. K. Zvonkin, <a href="/A005316/a005316_1.pdf">Plane and projective meanders</a>, Séries Formelles et Combinatoire Algébrique. Laboratoire Bordelais de Recherche Informatique, Université Bordeaux I, 1991, pp. 287-303. (Annotated scanned copy) %t A006657 A008828 = Import["https://oeis.org/A008828/b008828.txt", "Table"][[All, 2]]; %t A006657 a[n_] := A008828[[(n^2 - n + 4)/2]]; %t A006657 a /@ Range[2, 20] (* _Jean-François Alcover_, Sep 25 2019 *) %Y A006657 Cf. A005315. %Y A006657 A column of triangle A008828. %K A006657 nonn,nice %O A006657 2,1 %A A006657 _N. J. A. Sloane_, _Simon Plouffe_ %E A006657 a(13)-a(20) from _Andrew Howroyd_, Nov 22 2015