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 A301940 #19 Sep 11 2023 09:09:36
%S A301940 2,16,110,416,1470,4128,9102,20240,40106,71312,127426,203056,336070,
%T A301940 491392,790126,1067160,1650530,2086720,3180030,3878952,5768170,
%U A301940 6771680,9871350,11231064,16241094,17936352,25665290,27729640,39210350,41583104,58341778,60751880,84510650
%N A301940 Number of closed meanders with 2n crossings and 6 digons.
%C A301940 A meander together with the horizontal line separates the plane into several connected components. Each component has a given number of edges which is always an even number. The digons (or bigons) are the faces with least number of edges, that is 2. Equivalently, the number of digons is the number of arches between adjacent sites ("minimal arches") where the two extremal ones are considered adjacent.
%H A301940 V. Delecroix, E. Goujard, P. Zograf, and A. Zorich, <a href="https://arxiv.org/abs/1705.05190">Enumeration of meanders and Masur-Veech volumes</a>, arXiv:1705.05190 [math.GT], 2017.
%H A301940 <a href="/index/Me#meander">Index entries for sequences related to meanders</a>
%F A301940 Known asymptotics: Sum_{n <= N} a(n) ~ 70 N^7/(9 Pi^6).
%Y A301940 A002618 is the number of closed meanders with 4 digons. A300901 is the number of closed meanders with 5 digons. A005315 is the total number of closed meanders.
%K A301940 nonn
%O A301940 3,1
%A A301940 _Vincent Delecroix_, Mar 29 2018