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A088943 a(n)=60*sum(1<=i<=j<=k<=n,i*j^2/k). 4

%I

%S 0,60,450,1790,5195,12419,25999,49399,87154,145014,230088,350988,

%T 517973,743093,1040333,1425757,1917652,2536672,3305982,4251402,

%U 5401551,6787991,8445371,10411571,12727846,15438970,18593380,22243320,26444985,31258665

%N a(n)=60*sum(1<=i<=j<=k<=n,i*j^2/k).

%C Always an integer. Can be expressed as a polynomial with rational coefficients of degree 5.

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6,-15,20,-15,6,-1).

%F G.f.: -x*(x^4-5*x^3+10*x^2-90*x-60) / (x-1)^6. - _Colin Barker_, Jun 15 2013

%t LinearRecurrence[{6,-15,20,-15,6,-1},{0,60,450,1790,5195,12419},30] (* _Harvey P. Dale_, Apr 25 2018 *)

%o (PARI) a(n)=60*sum(k=1,n,sum(j=1,k,sum(i=1,j,i*j^2/k)))

%Y Cf. A088941, A088942.

%K nonn,easy

%O 0,2

%A _Benoit Cloitre_, Oct 25 2003

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Last modified June 24 14:24 EDT 2021. Contains 345417 sequences. (Running on oeis4.)