This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A352986 #13 Apr 14 2022 02:40:51
%S A352986 1,0,0,1,1,1,2,9,65,514,4124,33498,281829,2628658,31130220,521900363,
%T A352986 11550872369,292093228523,7763038391586,210839178560483,
%U A352986 5844964107402065,168148032885913260,5206234971937519704,183267822341124743772,7684147885975909244473
%N A352986 a(n) = Sum_{k=0..floor(n/3)} k^(3*(n-3*k)).
%F A352986 G.f.: Sum_{k>=0} x^(3 * k) / (1 - k^3 * x).
%F A352986 a(n) ~ sqrt(2*Pi) * (n/(3*LambertW(exp(1)*n/3)))^(3*n + 1/2 - 3*n/LambertW(exp(1)*n/3)) / (3*sqrt(1 + LambertW(exp(1)*n/3))). - _Vaclav Kotesovec_, Apr 14 2022
%t A352986 a[0] = 1; a[n_] := Sum[k^(3*(n - 3*k)), {k, 0, Floor[n/3]}]; Array[a, 25, 0] (* _Amiram Eldar_, Apr 13 2022 *)
%o A352986 (PARI) a(n) = sum(k=0, n\3, k^(3*(n-3*k)));
%o A352986 (PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=0, N, x^(3*k)/(1-k^3*x)))
%Y A352986 Cf. A352945.
%K A352986 nonn,easy
%O A352986 0,7
%A A352986 _Seiichi Manyama_, Apr 13 2022