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A056324
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Number of reversible string structures with n beads using a maximum of five different colors.
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3
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1, 2, 4, 11, 32, 116, 455, 1993, 9134, 43580, 211659, 1041441, 5156642, 25640456, 127773475, 637624313, 3184387574, 15910947980, 79521737939, 397510726681, 1987259550002, 9935420646296, 49674470817195
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A string and its reverse are considered to be equivalent. Permuting the colors will not change the structure. Thus aabc, cbaa and bbac are all considered to be identical.
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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
| Use de Bruijn's generalization of Polya's enumeration theorem as discussed in reference.
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CROSSREFS
| Cf. A032122.
Sequence in context: A148171 A113774 A124504 * A056325 A103293 A123418
Adjacent sequences: A056321 A056322 A056323 * A056325 A056326 A056327
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KEYWORD
| nonn
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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