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A045898
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a(n) = one of five triples of directions in n-th triple of moves in the optimal solution of the Tower of Hanoi; it is a squarefree sequence over a five-letter alphabet.
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0
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1, 2, 1, 3, 1, 2, 4, 5, 1, 2, 1, 3, 1, 5, 4, 3, 1, 2, 1, 3, 1, 2, 4, 5, 1, 2, 4, 3, 1, 5, 4, 5, 1, 2, 1, 3, 1, 2, 4, 5, 1, 2, 1, 3, 1, 5, 4, 3, 1, 2, 1, 3, 1, 5, 4, 5, 1, 2, 4, 3, 1, 5, 4, 3, 1, 2, 1, 3, 1, 2, 4, 5, 1, 2, 1, 3, 1, 5, 4, 3, 1, 2, 1, 3, 1, 2, 4
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OFFSET
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1,2
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COMMENTS
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To construct a(n), consider the six consecutive terms A101608(6*n-5) through A101608(6*n) as a single string (e.g., for n=1 we have 121323, for n=2 we have 123132). Only five different strings occur, corresponding to the five letter alphabet used here. Apply the mapping 121323 -> 1, 123132 -> 2, 213123 -> 3, 123123 -> 4, 213132 -> 5. - Sean A. Irvine, Mar 24 2021
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REFERENCES
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Andreas M. Hinz, The Tower of Hanoi, in Algebras and combinatorics (Hong Kong, 1997), 277-289, Springer, Singapore, 1999.
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LINKS
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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