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%I #9 Jun 13 2015 00:50:34
%S -1,5,65,306,975,2479,5425,10660,19311,32825,53009,82070,122655,
%T 177891,251425,347464,470815,626925,821921,1062650,1356719,1712535,
%U 2139345,2647276,3247375,3951649,4773105,5725790,6824831,8086475,9528129
%N Sum_{k=0..n^2} (k^2 - n^2)/n.
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6,-15,20,-15,6,-1).
%F a(n) = n*(2*n^2-5)*(n^2+1)/6. - _Vladeta Jovovic_, Jun 15 2002
%F G.f.: -x*(x^4-11*x^3-20*x^2-11*x+1) / (x-1)^6. - _Colin Barker_, Sep 29 2014
%o (PARI) vector(100, n, sum(k=0, n^2, k^2-n^2)/n) \\ _Colin Barker_, Sep 29 2014
%Y Cf. A052459.
%K sign,easy
%O 1,2
%A _Robert G. Wilson v_, Jun 12 2002