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A088942
a(n)=60*sum(1<=i<=j<=k<=n,i^2*j/k).
4
0, 60, 390, 1450, 4045, 9421, 19361, 36281, 63326, 104466, 164592, 249612, 366547, 523627, 730387, 997763, 1338188, 1765688, 2295978, 2946558, 3736809, 4688089, 5823829, 7169629, 8753354, 10605230, 12757940, 15246720, 18109455, 21386775
OFFSET
0,2
COMMENTS
Always an integer. Can be expressed as a polynomial with rational coefficients of degree 5.
FORMULA
a(n) = n/120 * (96n^4 + 765n^3 + 2210n^2 + 2275n + 1354).
G.f.: x*(x^4-5*x^3+10*x^2+30*x+60) / (x-1)^6. - Colin Barker, Jun 15 2013
PROG
(PARI) a(n)=60*sum(k=1, n, sum(j=1, k, sum(i=1, j, i^2*j/k)))
CROSSREFS
Sequence in context: A056428 A056419 A060489 * A135037 A020868 A223461
KEYWORD
nonn,easy
AUTHOR
Benoit Cloitre, Oct 25 2003
STATUS
approved