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.

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.

Terms

    a(0) =0a(1) =1a(2) =2a(3) =5a(4) =12a(5) =31a(6) =82a(7) =218a(8) =612a(9) =1673a(10) =4892a(11) =13672a(12) =41192a(13) =117194a(14) =361302a(15) =1042970a(16) =3274712a(17) =9567393a(18) =30490688a(19) =89984282a(20) =290353456

External references