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 A300901 #34 Jun 22 2018 04:03:52
%S A300901 16,40,168,280,544,1152,1560,2640,3504,5824,6552,12000,11456,19176,
%T A300901 18648,31312,30640,50064,43736,71392,62304,104800,87672,141048,121968,
%U A300901 191632,154200,255192,209536,327360,265880,435960,328176,533688,419064,649272,525280
%N A300901 Number of closed meanders with 2n crossings and 5 digons.
%C A300901 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 A300901 Vincent Delecroix, <a href="/A300901/b300901.txt">Table of n, a(n) for n = 4..164</a>
%H A300901 V. Delecroix, E. Goujard, P. Zograf, 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 A300901 <a href="/index/Me#meander">Index entries for sequences related to meanders</a>
%F A300901 Known asymptotics: Sum_{n <= N} a(n) ~ 16 N^5/(3 Pi^4).
%Y A300901 A002618 is the number of closed meanders with 4 digons. A301940 is the number of meanders with 6 digons. A005315 is the total number of closed meanders.
%K A300901 nonn
%O A300901 4,1
%A A300901 _Vincent Delecroix_, Mar 14 2018