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A056333
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Number of primitive (aperiodic) reversible string structures with n beads using a maximum of four different colors.
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2
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1, 1, 3, 9, 30, 102, 378, 1440, 5607, 22155, 87978, 350775, 1400490, 5597487, 22379145, 89498880, 357952170, 1431737433, 5726775978, 22906819575, 91626580269, 366505186047, 1466017950378, 5864067254880
(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
| Sum mu(d)*A056323(n/d) where d|n.
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CROSSREFS
| Cf. A056315.
Sequence in context: A148947 A090573 A048119 * A148948 A148949 A148950
Adjacent sequences: A056330 A056331 A056332 * A056334 A056335 A056336
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KEYWORD
| nonn
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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