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A121286
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Number of catacondensed hexagonal systems with n hexagons.
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1
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1, 3, 9, 26, 72, 192, 496, 1248, 3072, 7424, 17664, 41472, 96256, 221184, 503808, 1130496, 2555904, 5701632
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| Tosic R., Masulovic D., Stojmenovic I., Brunvoll J., Cyvin B. N. and Cyvin S. J., Enumeration of polyhex hydrocarbons to h = 17, J. Chem. Inf. Comput. Sci., 1995, 35, 181-187.
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FORMULA
| Except for a(16), this sequence has the recursion formula a(n)=6a(n-1)-12a(n-2)+8a(n-3). - T. D. Noe (noe(AT)sspectra.com), Nov 07 2006
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EXAMPLE
| If n=5 then the number of catacondensed hexagonal systems with n hexagons is 72 which is the fifth term in the sequence.
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CROSSREFS
| Sequence in context: A034531 A048470 A138237 * A072863 A054963 A118046
Adjacent sequences: A121283 A121284 A121285 * A121287 A121288 A121289
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KEYWORD
| nonn
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AUTHOR
| Parthasarathy Nambi (PachaNambi(AT)yahoo.com), Sep 06 2006
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