A046721 Number of semi-meanders of order n with 2 components.

1, 2, 6, 16, 48, 140, 428, 1308, 4072, 12796, 40432, 129432, 413900, 1342580, 4335288, 14201804, 46226896, 152594276, 500016036, 1660630740, 5472190206, 18264517264, 60475691308, 202684618564, 673892675030, 2266436498400, 7562707682032, 25510762766704, 85394319699916

Offset: 2

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 2..40
• P. Di Francesco, O. Golinelli and E. Guitter, Meander, folding and arch statistics, arXiv:hep-th/9506030, 1995.

Crossrefs

Cf. A000682, A046726.

Extensions

a(15)-a(30) from Andrew Howroyd, Nov 27 2015