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A122656
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n*floor(n/2)^2.
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2
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0, 0, 2, 3, 16, 20, 54, 63, 128, 144, 250, 275, 432, 468, 686, 735, 1024, 1088, 1458, 1539, 2000, 2100, 2662, 2783, 3456, 3600, 4394, 4563, 5488, 5684, 6750, 6975, 8192, 8448, 9826, 10115, 11664, 11988, 13718, 14079, 16000, 16400, 18522, 18963, 21296, 21780
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OFFSET
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0,3
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COMMENTS
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Szeged index of cycle of length n.
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REFERENCES
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J. Zerovnik, Szeged index of symmetric graphs, J. Chem. Inf. Comput. Sci., 39 (1999), 77-80.
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LINKS
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FORMULA
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a(n) = (n*(1-(-1)^n+2*(-1+(-1)^n)*n+2*n^2))/8. G.f.: x^2*(x^4+x^3+7*x^2+x+2) / ((x-1)^4*(x+1)^3). - Colin Barker, Sep 20 2013
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MATHEMATICA
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Table[n Floor[n/2]^2, {n, 0, 50}] (* or *) LinearRecurrence[ {1, 3, -3, -3, 3, 1, -1}, {0, 0, 2, 3, 16, 20, 54}, 50] (* Harvey P. Dale, May 31 2014 *)
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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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