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A056500
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Number of primitive (period n) periodic palindromes using exactly four different symbols.
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2
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0, 0, 0, 0, 0, 12, 24, 132, 240, 900, 1560, 4968, 8400, 24588, 40824, 113520, 186480, 502248, 818520, 2157360, 3497976, 9085452, 14676024, 37723260, 60780720, 155082900, 249401640, 632947728, 1016542800, 2569816476, 4123173624, 10393520640
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OFFSET
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1,6
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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. [See A056391 for pdf file of Chap. 2]
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LINKS
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FORMULA
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a(n) = Sum_{d|n} mu(d)*A056490(n/d).
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EXAMPLE
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For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome.
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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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