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 A078592 #9 Sep 20 2019 21:41:28
%S A078592 1,1,2,8,42,273,1970,15368,126510,1086546,9652364,88172609,824506191,
%T A078592 7865294687,76331857094,751981532942,7506432993145,75811326673326,
%U A078592 773682540353704,7969986193751019,82798726340037900,866804540900696571
%N A078592 Call two meanders from A005316 with 2n crossings equivalent if they differ by reflections in the X or Y axes. Sequence gives number of inequivalent meanders.
%C A078592 Symmetry group has order 4.
%H A078592 Jean-François Alcover, <a href="/A078592/b078592.txt">Table of n, a(n) for n = 0..27</a>
%F A078592 a(n) = (A005316(2n)+A005316(n))/2.
%t A078592 A005316 = Cases[Import["https://oeis.org/A005316/b005316.txt", "Table"], {_, _}][[All, 2]];
%t A078592 a[n_] := (A005316[[2 n + 1]] + A005316[[n + 1]])/2;
%t A078592 a /@ Range[0, 27] (* _Jean-François Alcover_, Sep 20 2019 *)
%K A078592 nonn
%O A078592 0,3
%A A078592 _N. J. A. Sloane_ and _Jon Wild_, Dec 08 2002