

A300901


Number of closed meanders with 2n crossings and 5 digons.


2



16, 40, 168, 280, 544, 1152, 1560, 2640, 3504, 5824, 6552, 12000, 11456, 19176, 18648, 31312, 30640, 50064, 43736, 71392, 62304, 104800, 87672, 141048, 121968, 191632, 154200, 255192, 209536, 327360, 265880, 435960, 328176, 533688, 419064, 649272, 525280
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OFFSET

4,1


COMMENTS

A meander together with the horizontal line separates the plane into several connected components. Each component has a given number of edges which is always an even number. The digons (or bigons) are the faces with least number of edges, that is 2. Equivalently, the number of digons is the number of arches between adjacent sites ("minimal arches") where the two extremal ones are considered adjacent.


LINKS



FORMULA

Known asymptotics: Sum_{n <= N} a(n) ~ 16 N^5/(3 Pi^4).


CROSSREFS

A002618 is the number of closed meanders with 4 digons. A301940 is the number of meanders with 6 digons. A005315 is the total number of closed meanders.


KEYWORD

nonn


AUTHOR



STATUS

approved



