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A056337
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Number of primitive (aperiodic) reversible string structures with n beads using exactly three different colors.
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0
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0, 0, 1, 4, 15, 49, 160, 498, 1544, 4715, 14356, 43420, 131145, 394990, 1188564, 3572400, 10732065, 32224216, 96733636, 290317660, 871200664, 2614083394, 7843255300, 23531731530, 70599259170, 211805771345
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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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
| A056332(n)-A056331(n).
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CROSSREFS
| Cf. A056319.
Sequence in context: A052201 A178704 A099167 * A053406 A143215 A132308
Adjacent sequences: A056334 A056335 A056336 * A056338 A056339 A056340
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KEYWORD
| nonn
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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