%I #11 Nov 19 2022 00:58:32
%S 0,1,2,5,12,31,82,218,612,1673,4892,13672,41192,117194,361302,1042970,
%T 3274712,9567393,30490688,89984282,290353456
%N 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 Cf. A005316, A076875 (undirected line), A076876, A076907 (end anywhere).
%K nonn,more,nice
%O 0,3
%A _N. J. A. Sloane_ and _Jon Wild_, Nov 26 2002
%E a(7) corrected Aug 25 2003
%E a(7) corrected and a(8)-a(20) added by _Robert Price_, Jul 29 2012