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

0,2

Comments

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

Links

Table of n, a(n) for n=0..29.

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

Formula

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

Mathematica

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

Prog

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

Crossrefs

Cf. A088941, A088942.

Sequence in context: A135037 A020868 A223461 * A097387 A057096 A246774

Adjacent sequences: A088940 A088941 A088942 * A088944 A088945 A088946

Keyword

nonn,easy

Author

Benoit Cloitre, Oct 25 2003

Status

approved