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A020874
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Number of paths in Moebius ladder M_n.
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4
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0, 3, 30, 135, 452, 1295, 3378, 8295, 19560, 44847, 100790, 223223, 488940, 1061775, 2289882, 4910535, 10480208, 22275695, 47178270, 99605847, 209704980, 440390223, 922733570, 1929364775, 4026514872
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OFFSET
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0,2
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REFERENCES
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J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.
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LINKS
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FORMULA
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a(n) = 10*n*2^n-n^3-5*n^2-11*n.
G.f.: -x*(8*x^4-20*x^3+27*x^2-6*x-3) / ((x-1)^4*(2*x-1)^2). - Colin Barker, Apr 05 2013
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MATHEMATICA
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CoefficientList[Series[- x (8 x^4 - 20 x^3 + 27 x^2 - 6 x - 3)/((x - 1)^4 (2*x - 1)^2), {x, 0, 30}], x] (* Vincenzo Librandi, Oct 16 2013 *)
LinearRecurrence[{8, -26, 44, -41, 20, -4}, {0, 3, 30, 135, 452, 1295}, 30] (* Harvey P. Dale, Apr 05 2018 *)
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PROG
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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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