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Search: id:A056324
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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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+0
4
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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; listen)
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OFFSET
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1,2
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COMMENT
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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
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M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia.
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FORMULA
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Use de Bruijn's generalization of Polya's enumeration theorem as discussed in reference.
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CROSSREFS
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Cf. A032122.
Sequence in context: A148171 A113774 A124504 this_sequence A056325 A103293 A123418
Adjacent sequences: A056321 A056322 A056323 this_sequence A056325 A056326 A056327
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KEYWORD
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nonn
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AUTHOR
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Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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