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A363639
Expansion of Sum_{k>0} (1/(1 - k*x^k)^3 - 1).
8
3, 12, 19, 51, 36, 180, 57, 405, 352, 918, 111, 3990, 144, 5064, 6534, 15945, 222, 51462, 267, 99354, 82478, 160812, 369, 808490, 66051, 861630, 1090342, 2593614, 552, 8966414, 621, 13039761, 13831470, 22415778, 3166218, 114011229, 852, 110103540, 167426822
OFFSET
1,1
FORMULA
a(n) = Sum_{d|n} (n/d)^d * binomial(d+2,2).
MATHEMATICA
a[n_] := DivisorSum[n, (n/#)^# * Binomial[# + 2, 2] &]; Array[a, 40] (* Amiram Eldar, Jul 17 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (n/d)^d*binomial(d+2, 2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 13 2023
STATUS
approved