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A056326
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Number of reversible string structures with n beads using exactly two different colors.
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1
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0, 1, 2, 5, 9, 19, 35, 71, 135, 271, 527, 1055, 2079, 4159, 8255, 16511, 32895, 65791, 131327, 262655, 524799, 1049599, 2098175, 4196351, 8390655, 16781311, 33558527, 67117055, 134225919, 268451839
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| A string and its reverse are considered to be equivalent. Permuting the colors will not change the structure.
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REFERENCES
| M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia.
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FORMULA
| A005418(n)-1.
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CROSSREFS
| Cf. A056309.
Sequence in context: A048082 A089089 A014495 * A122893 A178841 A062092
Adjacent sequences: A056323 A056324 A056325 * A056327 A056328 A056329
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KEYWORD
| nonn
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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