OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..387
FORMULA
G.f.: (1/(1 - x)) * Sum_{j>=1} Sum_{k>=1} k^(k-1) * x^(j*k) * (1 - x^j).
MATHEMATICA
a[n_] := Sum[Floor[n/k]^(Floor[n/k] - 1), {k, 1, n}]; Array[a, 20] (* Amiram Eldar, Jun 08 2021 *)
PROG
(PARI) a(n) = sum(k=1, n, (n\k)^(n\k-1));
(PARI) my(N=20, x='x+O('x^N)); Vec(sum(j=1, N, (1-x^j)*sum(k=1, N, k^(k-1)*x^(j*k)))/(1-x))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 07 2021
STATUS
approved