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

%I #20 Dec 12 2015 15:25:00

%S 1,2,6,16,48,140,428,1308,4072,12796,40432,129432,413900,1342580,

%T 4335288,14201804,46226896,152594276,500016036,1660630740,5472190206,

%U 18264517264,60475691308,202684618564,673892675030,2266436498400,7562707682032,25510762766704,85394319699916

%N Number of semi-meanders of order n with 2 components.

%H Andrew Howroyd, <a href="/A046721/b046721.txt">Table of n, a(n) for n = 2..40</a>

%H P. Di Francesco, O. Golinelli and E. Guitter, <a href="http://arXiv.org/abs/hep-th/9506030">Meander, folding and arch statistics</a>, arXiv:hep-th/9506030, 1995.

%Y Cf. A000682, A046726.

%K nonn

%O 2,2

%A _N. J. A. Sloane_

%E a(15)-a(30) from _Andrew Howroyd_, Nov 27 2015