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 A360775 #10 Feb 20 2023 07:50:45
%S A360775 1,1,4,28,260,3152,46913,826677,16823968,388245283,10016796672,
%T A360775 285699444297,8926107792609,303160590533808,11120927427841820,
%U A360775 438196895219227683,18457860168281435172,827678295600605015006,39364859979651634985089
%N A360775 Expansion of Sum_{k>=0} (x * (k + x^2))^k.
%F A360775 a(n) = Sum_{k=0..floor(n/3)} (n-2*k)^(n-3*k) * binomial(n-2*k,k).
%o A360775 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, (x*(k+x^2))^k))
%o A360775 (PARI) a(n) = sum(k=0, n\3, (n-2*k)^(n-3*k)*binomial(n-2*k, k));
%Y A360775 Cf. A360774, A360776.
%Y A360775 Cf. A360018, A360727.
%K A360775 nonn
%O A360775 0,3
%A A360775 _Seiichi Manyama_, Feb 20 2023