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A056505
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Number of periodic palindromic structures using a maximum of four different symbols.
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5
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1, 1, 2, 2, 5, 5, 13, 15, 40, 51, 133, 187, 479, 715, 1815, 2795, 7036, 11051, 27747, 43947, 110061, 175275, 438683, 700075, 1750959, 2798251, 6997643, 11188907, 27975351, 44747435, 111876715, 178973355, 447445692, 715860651, 1789684267, 2863377067, 7158491875
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OFFSET
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0,3
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COMMENTS
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For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure.
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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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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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a(0)=1 prepended and terms a(17) and beyond from Andrew Howroyd, Oct 01 2019
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STATUS
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approved
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