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 A085919 #7 Mar 31 2012 10:32:24 %S A085919 3,0,3,1,9,6,45,42,279,320,1977,2610,15306,22404,126300,200158, %T A085919 1093515,1846314,9830547,17481864 %N A085919 Number of ways a loop can cross three roads meeting in a Y n times. %C A085919 The Mercedes-Benz problem: closed meanders crossing a Y. %H A085919 Anonymous, <a href="/A078105/a078105.a.gif">Illustration for a(3) = 1</a> %e A085919 With three crossings the loop must cut each road exactly once, so a(3) = 1. %Y A085919 Similar to A078104, but without the constraint of touching the (-, -) quadrant. %K A085919 nonn %O A085919 0,1 %A A085919 _N. J. A. Sloane_ and _Jon Wild_, Aug 25 2003