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 A301940 Number of closed meanders with 2n crossings and 6 digons. 1
 2, 16, 110, 416, 1470, 4128, 9102, 20240, 40106, 71312, 127426, 203056, 336070, 491392, 790126, 1067160, 1650530, 2086720, 3180030, 3878952, 5768170, 6771680, 9871350, 11231064, 16241094, 17936352, 25665290, 27729640, 39210350, 41583104, 58341778, 60751880, 84510650 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 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 V. Delecroix, E. Goujard, P. Zograf, A. Zorich Enumeration of meanders and Masur-Veech volumes, arXiv:1705.05190 [math.GT], 2017. FORMULA Known asymptotics: Sum_{n <= N} a(n) ~ 70 N^7/(9 Pi^6). CROSSREFS A002618 is the number of closed meanders with 4 digons. A300901 is the number of closed meanders with 5 digons. A005315 is the total number of closed meanders. Sequence in context: A329550 A208137 A207435 * A058121 A117627 A117628 Adjacent sequences:  A301937 A301938 A301939 * A301941 A301942 A301943 KEYWORD nonn AUTHOR Vincent Delecroix, Mar 29 2018 STATUS approved

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Last modified July 29 09:41 EDT 2021. Contains 346344 sequences. (Running on oeis4.)