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

0, 60, 450, 1790, 5195, 12419, 25999, 49399, 87154, 145014, 230088, 350988, 517973, 743093, 1040333, 1425757, 1917652, 2536672, 3305982, 4251402, 5401551, 6787991, 8445371, 10411571, 12727846, 15438970, 18593380, 22243320, 26444985, 31258665

Offset: 0

Author

Benoit Cloitre, Oct 25 2003

Keywords

• nonn
• easy

Comments

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

Links

• Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

Crossrefs

Cf. A088941, A088942.

Programs

Mathematica

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

PARI

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

Formula

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