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A304164
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a(n) = 27*n^2 - 21*n + 6 (n>=1).
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4
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12, 72, 186, 354, 576, 852, 1182, 1566, 2004, 2496, 3042, 3642, 4296, 5004, 5766, 6582, 7452, 8376, 9354, 10386, 11472, 12612, 13806, 15054, 16356, 17712, 19122, 20586, 22104, 23676, 25302, 26982, 28716, 30504, 32346, 34242, 36192, 38196, 40254, 42366
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OFFSET
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1,1
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COMMENTS
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a(n) is the number of edges in the HcDN1(n) network (see Fig. 3 in the Hayat et al. manuscript).
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LINKS
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FORMULA
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G.f.: 6*x*(2 + 6*x + x^2)/(1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 3. (End)
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MAPLE
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seq(27*n^2-21*n+6, n = 1 .. 40);
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PROG
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(PARI) a(n) = 27*n^2-21*n+6; \\ Altug Alkan, May 09 2018
(PARI) Vec(6*x*(2 + 6*x + x^2) / (1 - x)^3 + O(x^60)) \\ Colin Barker, May 10 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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