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A304830
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a(n) = 102*2^n - 108 (n>=1).
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2
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96, 300, 708, 1524, 3156, 6420, 12948, 26004, 52116, 104340, 208788, 417684, 835476, 1671060, 3342228, 6684564, 13369236, 26738580, 53477268, 106954644, 213909396, 427818900, 855637908, 1711275924, 3422551956, 6845104020, 13690208148, 27380416404, 54760832916, 109521665940, 219043331988
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OFFSET
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1,1
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COMMENTS
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a(n) is the first Zagreb index of the dendrimer molecule D[n] defined in the Ashrafi et al. reference.
The first Zagreb index of a simple connected graph is the sum of the squared degrees of its vertices. Alternatively, it is the sum of the degree sums d(i) + d(j) over all edges ij of the graph.
The M-polynomial of the dendrimer molecule D[n] is M(D[n]; x,y) = 6*2^n*x^2*y^2 + 6(2*2^n - 3)*x^2*y^3 + 3*(2^n - 1)*x^3*y^3.
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LINKS
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FORMULA
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G.f.: 12*x*(8 + x) / ((1 - x)*(1 - 2*x)).
a(n) = 3*a(n-1) - 2*a(n-2) for n>2.
(End)
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MAPLE
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seq(102*2^n-108, n = 1 .. 35);
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MATHEMATICA
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Table[102*2^n-108, {n, 40}] (* or *) LinearRecurrence[{3, -2}, {96, 300}, 40] (* Harvey P. Dale, Jan 07 2022 *)
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PROG
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(PARI) Vec(12*x*(8 + x) / ((1 - x)*(1 - 2*x)) + O(x^40)) \\ Colin Barker, May 20 2018
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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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