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A056470
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Number of palindromic structures using a maximum of five different symbols.
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5
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1, 1, 2, 2, 5, 5, 15, 15, 52, 52, 202, 202, 855, 855, 3845, 3845, 18002, 18002, 86472, 86472, 422005, 422005, 2079475, 2079475, 10306752, 10306752, 51263942, 51263942, 255514355, 255514355, 1275163905
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OFFSET
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1,3
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COMMENTS
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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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a(2n-1) = a(2n) = A056272(n). [R. J. Mathar, Nov 24 2010]
G.f.: -x*(19*x^6-24*x^4+9*x^2-1) / ((x-1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [Colin Barker, Dec 05 2012]
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MATHEMATICA
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LinearRecurrence[{1, 10, -10, -31, 31, 30, -30}, {1, 1, 2, 2, 5, 5, 15}, 40] (* Harvey P. Dale, Dec 16 2017 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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