OFFSET
0,3
FORMULA
G.f.: exp(Sum_{k>=1} x^k * Sum_{d|k} (-1)^(d+1) / (d * (1 - k/d * x)^d)).
MATHEMATICA
m = 27; CoefficientList[Series[Product[1 + x^k/(1 - k*x), {k, 1, m}], {x, 0, m}], x] (* Amiram Eldar, Aug 10 2020 *)
PROG
(PARI) N=40; x='x+O('x^N); Vec(prod(k=1, N, 1+x^k/(1-k*x)))
(PARI) N=40; x='x+O('x^N); Vec(exp(sum(k=1, N, x^k*sumdiv(k, d, (-1)^(d+1)/(d*(1-k/d*x)^d)))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 10 2020
STATUS
approved