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Number of semi-meanders of order n with 3 components.
2

%I #25 Jul 15 2019 04:59:18

%S 1,3,11,37,126,430,1454,4976,16880,57824,197010,675428,2310268,

%T 7927778,27205180,93448486,321537086,1105589516,3812424912,

%U 13121988240,45330375774,156172996170,540314673678,1863197292582,6454265995454,22275589419432,77246945788890,266813803179348

%N Number of semi-meanders of order n with 3 components.

%H Andrew Howroyd, <a href="/A046722/b046722.txt">Table of n, a(n) for n = 3..40</a>

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

%H P. Di Francesco, O. Golinelli, and E. Guitter, <a href="https://doi.org/10.1016/S0895-7177(97)00202-1">Meander, folding and arch statistics</a>, Mathematical and Computer Modelling 26 (1997), 97-147.

%Y Cf. A000682, A046726.

%K nonn

%O 3,2

%A _N. J. A. Sloane_

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