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A103334
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Number of closed walks of length 2n at any of the nodes of degree 1 on the graph of the (7,4) Hamming code.
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3
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1, 1, 4, 24, 176, 1376, 10944, 87424, 699136, 5592576, 44739584, 357914624, 2863312896, 22906494976, 183251943424, 1466015514624, 11728124051456, 93824992280576, 750599937982464, 6004799503335424, 48038396025634816
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OFFSET
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0,3
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COMMENTS
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a(n+1)=8^n/3+2^(n+1)/3 with g.f. (1-6x)/(1-10x+16x^2) counts walks of length 2n+1 between adjacent nodes of degrees 1 and 4 on the graph of the (7,4) Hamming code.
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REFERENCES
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David J.C. Mackay, Information Theory, Inference and Learning Algorithms, CUP, 2003, p. 19.
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LINKS
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FORMULA
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G.f.: (1-9x+10x^2)/(1-10x+16x^2); a(n)=8^(n-1)/3+2^(n)/3+5*0^n/8.
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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