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A368956
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a(n) = 3^n - 2^(n+1) - 1.
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1
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-2, 0, 10, 48, 178, 600, 1930, 6048, 18658, 57000, 173050, 523248, 1577938, 4750200, 14283370, 42915648, 128878018, 386896200, 1161212890, 3484687248, 10456158898, 31372671000, 94126401610, 282395982048, 847221500578, 2541731610600, 7625329049530
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OFFSET
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1,1
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COMMENTS
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For even n >= 4, also the number of minimum vertex colorings of the n-Moebius ladder.
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LINKS
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FORMULA
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a(n) = 6*(n-1) - 11*a(n-2) + 6*a(n-3).
G.f.: 2*x*(1-6*x+6*x^2)/((-1+x)*(-1+2*x)*(-1+3*x)).
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MATHEMATICA
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Table[3^n - 2^(n + 1) - 1, {n, 20}]
LinearRecurrence[{6, -11, 6}, {-2, 0, 10}, 20]
CoefficientList[Series[2 (1 - 6 x + 6 x^2)/((-1 + x) (-1 + 2 x) (-1 + 3 x)), {x, 0, 20}], x]
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PROG
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(Python)
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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