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 A380021 #7 Jan 09 2025 08:00:16
%S A380021 1,2,9,77,977,16281,335173,8208901,233037185,7522621505,272096862821,
%T A380021 10899761462085,478990330829233,22910468287983121,1184832950732237381,
%U A380021 65877062190857942981,3918656527419803705729,248317978064709144523521,16699787528059828201246021
%N A380021 Expansion of e.g.f. 1/(exp(-3*x) - 3*x*exp(-2*x))^(1/3).
%F A380021 a(n) = n! * Sum_{k=0..n} (-3)^k * (k+1)^(n-k) * binomial(-1/3,k)/(n-k)!.
%o A380021 (PARI) a(n) = n!*sum(k=0, n, (-3)^k*(k+1)^(n-k)*binomial(-1/3, k)/(n-k)!);
%Y A380021 Cf. A380016, A380017.
%K A380021 nonn
%O A380021 0,2
%A A380021 _Seiichi Manyama_, Jan 09 2025