OFFSET
1,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..387
FORMULA
G.f.: Sum_{k>=1} (-k)^(k-1)*x^k * (1 - (-k*x)^k)/((1 - (-k)^(k-1)*x^k) * (1 + k*x)).
MATHEMATICA
a[n_] := Sum[(-k)^(n - Floor[n/k]), {k, 1, n}]; Array[a, 20] (* Amiram Eldar, Jun 08 2021 *)
PROG
(PARI) a(n) = sum(k=1, n, (-k)^(n-n\k));
(PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, (-k)^(k-1)*x^k*(1-(-k*x)^k)/((1-(-k)^(k-1)*x^k)*(1+k*x))))
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jun 08 2021
STATUS
approved