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 A076906 #11 Nov 19 2022 00:58:32 %S A076906 0,1,2,5,12,31,82,218,612,1673,4892,13672,41192,117194,361302,1042970, %T A076906 3274712,9567393,30490688,89984282,290353456 %N A076906 Meandric numbers for a river (or directed line) crossing two perpendicular roads at n points, beginning in the (-,-) quadrant and ending in the (+,+) quadrant if n even, in the (+,-) quadrant if n odd. %Y A076906 Cf. A005316, A076875 (undirected line), A076876, A076907 (end anywhere). %K A076906 nonn,more,nice %O A076906 0,3 %A A076906 _N. J. A. Sloane_ and _Jon Wild_, Nov 26 2002 %E A076906 a(7) corrected Aug 25 2003 %E A076906 a(7) corrected and a(8)-a(20) added by _Robert Price_, Jul 29 2012