A352984 a(n) = Sum_{k=0..floor(n/3)} k^(3*n).

1, 0, 0, 1, 1, 1, 262145, 2097153, 16777217, 7625731702716, 205892205836474, 5559069156490116, 4722516577573661689554, 302235507459360068466700, 19342922532827596354169130, 28422947373397605556855075614825, 3552792907042781637051562368414979

Offset: 0

Author

Seiichi Manyama, Apr 13 2022

Keywords

• nonn
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..185

Crossrefs

Cf. A352983.

Programs

Mathematica

a[0] = 1; a[n_] := Sum[k^(3*n), {k, 0, Floor[n/3]}]; Array[a, 16, 0] (* Amiram Eldar, Apr 13 2022 *)

PARI

a(n) = sum(k=0, n\3, k^(3*n));

PARI

my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, (k^3*x)^(3*k)/(1-k^3*x)))

Formula

G.f.: Sum_{k>=0} (k^3 * x)^(3 * k) / (1 - k^3 * x).