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 A076875 #10 Jul 30 2012 00:44:18 %S A076875 1,2,4,10,22,62,176,436 %N A076875 Meandric numbers for a curve crossing two perpendicular lines at n points. %C A076875 a(n) = number of ways that a curve can start in the (-,-) quadrant, cross the x and y axes at exactly n points and end in any quadrant. Line is undirected. %H A076875 Jon Wild, <a href="/A076875/a076875.gif">Illustration of a(4) = 22</a> (ignore the arrowheads) %F A076875 For n odd a(n) = 2*A076906(n). %e A076875 See illustration for a(4)=22: each of the 12 solutions shown crosses the x-axis first and ten of them are related by mirror symmetry to a corresponding curve that crosses the y-axis first, making the total a(4)=22. %Y A076875 Cf. A005316, A076876, A076906, A076907 (directed case). %K A076875 nonn,nice %O A076875 0,2 %A A076875 _N. J. A. Sloane_ and _Jon Wild_, Nov 24 2002 %E A076875 a(6) and a(7) corrected Aug 23 2003 %E A076875 a(7) corrected by _Robert Price_, Jul 29 2012