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A362518
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Number of vertex cuts in the n-helm graph.
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0
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1, 12, 71, 354, 1617, 7020, 29563, 122214, 499493, 2026848, 8186895, 32969754, 132508729, 531842196, 2132610467, 8545773774, 34228238925, 137046552264, 548583066679, 2195514451074, 8785586531681, 35152894560252, 140643143849931, 562667104454454, 2250951652660597
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OFFSET
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1,2
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COMMENTS
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Sequence extended to n = 1 using the formula/recurrence.
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LINKS
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FORMULA
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a(n) = (2^n - 1)*(1 + 2^(n + 1) - n) - 3^n.
a(n) = 13*a(n-1)-67*a(n-2)+175*a(n-3)-244*a(n-4)+172*a(n-5)-48*a(n-6).
G.f.: x*(1 - x - 18*x^2 + 60*x^3 - 84*x^4 + 48*x^5)/((-1 + x)^2*(-1 + 2*x)^2*(-1 + 3*x)*(-1 + 4*x)).
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MATHEMATICA
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Table[(2^n - 1) (1 + 2^(n + 1) - n) - 3^n, {n, 20}]
LinearRecurrence[{13, -67, 175, -244, 172, -48}, {1, 12, 71, 354, 1617, 7020}, 20]
CoefficientList[Series[(1 - x - 18 x^2 + 60 x^3 - 84 x^4 + 48 x^5)/((-1 + x)^2 (-1 + 2 x)^2 (-1 + 3 x) (-1 + 4 x)), {x, 0, 20}], x]
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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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EXTENSIONS
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STATUS
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approved
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