A046723 Number of semi-meanders of order n with 4 components.

1, 4, 17, 66, 254, 956, 3584, 13256, 49052, 179552, 658560, 2394504, 8724464, 31575096, 114451388, 412811544, 1490190544, 5360943684, 19288139802, 69245171564, 248463024330, 890477645192, 3188033497580, 11409453277272, 40771092374710, 145735210316376, 519955750491512

Offset: 4

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 4..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(40) from Andrew Howroyd, Dec 07 2015