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A277987
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a(n) = 100*n - 28.
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1
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-28, 72, 172, 272, 372, 472, 572, 672, 772, 872, 972, 1072, 1172, 1272, 1372, 1472, 1572, 1672, 1772, 1872, 1972, 2072, 2172, 2272, 2372, 2472, 2572, 2672, 2772, 2872, 2972, 3072, 3172, 3272, 3372, 3472, 3572, 3672, 3772, 3872, 3972
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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 second Zagreb index of the tetrameric 1,3-adamantane TA[n]. The second Zagreb index of a simple connected graph is the sum of the degree products d(i)d(j) over all edges ij of the graph. The pictorial definition of the tetrameric 1,3-adamantane can be viewed in the G. H. Fath-Tabar et al. reference.
The M-polynomial of the tetrameric 1,3-adamantane TA[n] is M(TA[n],x,y) = 6*(n+1)*x^2*y^3 + 6*(n-1)*x^2*y^4 + (n-1)*x^4*y^4.
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LINKS
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FORMULA
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G.f.: 4*(32*x - 7)/(1 - x)^2.
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MAPLE
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seq(100*n-28, n = 0..40);
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MATHEMATICA
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100*Range[0, 40]-28 (* or *) LinearRecurrence[{2, -1}, {-28, 72}, 50] (* Harvey P. Dale, Feb 13 2018 *)
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PROG
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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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