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Meandric numbers for a river (or directed line) crossing two perpendicular roads at n points, beginning in the (-,-) quadrant, crossing x axis first and ending in any quadrant.
2

%I #12 Aug 14 2012 15:50:27

%S 0,1,3,5,16,31,105,218,770,1673,6096,13672,51027,117194,445787,

%T 1042970,4028922,9567393,37432324,89984282,355854272

%N Meandric numbers for a river (or directed line) crossing two perpendicular roads at n points, beginning in the (-,-) quadrant, crossing x axis first and ending in any quadrant.

%Y Similar to A076907 but must cross x axis first.

%K nonn,more

%O 0,3

%A _N. J. A. Sloane_ and _Jon Wild_, Aug 25 2003

%E a(7) corrected by _Robert Price_, Jul 29 2012

%E a(8)-a(20) from _Robert Price_, Aug 14 2012