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A305267
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a(n) = 68*2^n + 358.
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3
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426, 494, 630, 902, 1446, 2534, 4710, 9062, 17766, 35174, 69990, 139622, 278886, 557414, 1114470, 2228582, 4456806, 8913254, 17826150, 35651942, 71303526, 142606694, 285213030, 570425702, 1140851046, 2281701734, 4563403110, 9126805862, 18253611366, 36507222374, 73014444390, 146028888422
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OFFSET
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0,1
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COMMENTS
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For n>=1, a(n) is the first Zagreb index of the first type of dendrimer nanostar G[n], shown pictorially in the Iranmanesh et al. reference (Fig. 1).
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 nanostar G[n] is M(G[n]; x, y) = (4*2^n + 23)*x^2*y^2 + (8*2^n + 34)*x^2*y^3 +(2*2^n +16)*x^3*y^3.
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LINKS
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FORMULA
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MAPLE
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seq(68*2^n+358, n = 0..40);
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MATHEMATICA
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LinearRecurrence[{3, -2}, {426, 494}, 40] (* Harvey P. Dale, Mar 22 2019 *)
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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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