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 A076907 #12 Aug 01 2012 12:31:57 %S A076907 2,2,6,10,32,62,210,436,1540,3346,12192,27344,102054,234388,891574, %T A076907 2085940,8057844,19134786,74864648,179968564,711708544 %N A076907 Meandric numbers for a river crossing two perpendicular roads at n points, beginning in the (-,-) quadrant and ending in any quadrant. %C A076907 a(n) = number of ways that a directed curve (or arrow) can start in the (-,-) quadrant, cross the x and y axes at exactly n points and end in any quadrant. %F A076907 a(2n+1) = 2*A076906(2n+1). %Y A076907 Cf. A005316, A076876, A076906, A076875 (undirected case). %Y A076907 Cf. A077551 (cross x axis first). %K A076907 nonn,more %O A076907 0,1 %A A076907 _N. J. A. Sloane_ and _Jon Wild_, Nov 26 2002 %E A076907 a(6) and a(7) corrected Aug 25 2003 %E A076907 a(7) corrected by _Robert Price_, Jul 29 2012 %E A076907 a(8)-a(20) from _Robert Price_, Aug 01 2012