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A220867
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Number of perfect matchings in the twisted graph (C_4 X C_n)_(1234).
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1
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2, 14, 80, 194, 888, 2702, 11040, 37634, 146024, 524174, 1988720, 7300802, 27436248, 101687054, 380604480, 1416317954, 5292200648, 19726764302, 73658763920, 274758382274
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical g.f.: -2 * x * ( 3*x^6 - 11*x^5 - 19*x^4 + 74*x^3 - 7*x^2 - 3*x - 1 ) / ( (x^2 - 4*x + 1) * (x^2 - 2*x - 1) * (x^2 + 2*x - 1) ). - Joerg Arndt, Nov 17 2015
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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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