OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: exp( - Sum_{k>=1} x^k * Sum_{d|k} (1 + k/d * x)^d / d).
MATHEMATICA
m = 47; CoefficientList[Series[Product[1 - x^k*(1 + k*x), {k, 1, m}], {x, 0, m}], x] (* Amiram Eldar, May 01 2021 *)
PROG
(PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, 1-x^k*(1+k*x)))
(PARI) N=66; x='x+O('x^N); Vec(exp(-sum(k=1, N, x^k*sumdiv(k, d, (1+k/d*x)^d/d))))
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Aug 09 2020
STATUS
approved