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Search: id:A060972
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| A060972 |
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Triangle giving numbers of closed plane meanders. |
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+0
1
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| 1, 1, 1, 1, 6, 1, 1, 20, 20, 1, 1, 50, 160, 50, 1, 1, 105, 808, 808, 105, 1
(list; table; graph; listen)
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OFFSET
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1,5
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COMMENT
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This counts closed plane meanders according to the number of white regions when regions are colored black and white alternatively. So the sum of each line is given by A005315. The outer column is constant equal to 1. The next-to-outer column is given by A002415
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REFERENCES
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Franz, Reinhard O. W. and Earnshaw, Berton A. A constructive enumeration of meanders. Ann. Comb. 6 (2002), no. 1, 7-17.
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EXAMPLE
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{1}, {1, 1}, {1, 6, 1}, {1, 20, 20, 1}, {1, 50, 160, 50, 1}, {1, 105, 808, 808, 105, 1}
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CROSSREFS
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Row sums give A005315, diagonals give A002415, A079555, A079556
Sequence in context: A141690 A146957 A146988 this_sequence A144066 A056941 A157638
Adjacent sequences: A060969 A060970 A060971 this_sequence A060973 A060974 A060975
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KEYWORD
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more,nonn,tabl
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AUTHOR
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Frederic Chapoton (chapoton(AT)math.jussieu.fr), May 09 2001
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EXTENSIONS
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Franz and Earnshaw give the first 14 rows.
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