OFFSET
0,2
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).
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
KEYWORD
nonn,easy
AUTHOR
Benoit Cloitre, Oct 25 2003
STATUS
approved