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 A046723 #13 Mar 07 2020 21:28:52 %S A046723 1,4,17,66,254,956,3584,13256,49052,179552,658560,2394504,8724464, %T A046723 31575096,114451388,412811544,1490190544,5360943684,19288139802, %U A046723 69245171564,248463024330,890477645192,3188033497580,11409453277272,40771092374710,145735210316376,519955750491512 %N A046723 Number of semi-meanders of order n with 4 components. %H A046723 Andrew Howroyd, <a href="/A046723/b046723.txt">Table of n, a(n) for n = 4..40</a> %H A046723 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. %Y A046723 Cf. A000682, A046726. %K A046723 nonn %O A046723 4,2 %A A046723 _N. J. A. Sloane_ %E A046723 a(15)-a(40) from _Andrew Howroyd_, Dec 07 2015