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 A360730 #12 Feb 18 2023 19:00:30
%S A360730 1,1,4,28,272,3368,50768,902397,18481408,428556075,11099001600,
%T A360730 317544062217,9946366838784,338537433281448,12441407233436672,
%U A360730 491002325860132371,20710640842719301632,929821866165431838038,44270378887441746923520
%N A360730 Expansion of Sum_{k>=0} (k * x * (1 + k*x^2))^k.
%H A360730 Winston de Greef, <a href="/A360730/b360730.txt">Table of n, a(n) for n = 0..385</a>
%F A360730 a(n) = Sum_{k=0..floor(n/3)} (n-2*k)^(n-k) * binomial(n-2*k,k).
%o A360730 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, (k*x*(1+k*x^2))^k))
%o A360730 (PARI) a(n) = sum(k=0, n\3, (n-2*k)^(n-k)*binomial(n-2*k, k));
%Y A360730 Cf. A360618, A360731.
%K A360730 nonn
%O A360730 0,3
%A A360730 _Seiichi Manyama_, Feb 18 2023