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0, 4, 32, 108, 256, 500, 864, 1372, 2048, 2916, 4000, 5324, 6912, 8788, 10976, 13500, 16384, 19652, 23328, 27436, 32000, 37044, 42592, 48668, 55296, 62500, 70304, 78732, 87808, 97556, 108000, 119164, 131072, 143748, 157216, 171500, 186624, 202612, 219488
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refs;
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internal format)
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OFFSET
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0,2
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COMMENTS
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2*a(n) = (2*n)^3 is a perfect cube.
Number of edges of the product of two complete bipartite graphs, each of order 2n, K_n,n x K_n,n - Roberto E. Martinez II, Jan 07 2002
For n>=3, also the detour index of the n-gear graph. - Eric W. Weisstein, Dec 20 2017
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LINKS
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FORMULA
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E.g.f.: 4*x*(1 + 3*x + x^2)*exp(x).
Sum_{n>=1} 1/a(n) = zeta(3)/4. (End)
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {0, 4, 32, 108}, 40] (* Harvey P. Dale, Sep 07 2016 *)
CoefficientList[Series[(4 x (1 + 4 x + x^2))/(-1 + x)^4, {x, 0, 20}], x] (* Eric W. Weisstein, Dec 20 2017 *)
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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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