A077551 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.

0, 1, 3, 5, 16, 31, 105, 218, 770, 1673, 6096, 13672, 51027, 117194, 445787, 1042970, 4028922, 9567393, 37432324, 89984282, 355854272

Offset

0,3

Links

Table of n, a(n) for n=0..20.

Crossrefs

Similar to A076907 but must cross x axis first.

Sequence in context: A370604 A295358 A369930 * A106588 A123785 A121646

Adjacent sequences: A077548 A077549 A077550 * A077552 A077553 A077554

Keyword

nonn,more

Author

N. J. A. Sloane and Jon Wild, Aug 25 2003

Extensions

a(7) corrected by Robert Price, Jul 29 2012

a(8)-a(20) from Robert Price, Aug 14 2012

Status

approved