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 A370931 #13 Mar 06 2024 07:59:44
%S A370931 1,1,4,30,340,5180,99360,2300830,62473600,1946941920,68507714800,
%T A370931 2686816932800,116225776497600,5497681373384200,282305750023897600,
%U A370931 15640212734095950000,929908726447266966400,59061538103044360083200,3990922849835432102592000
%N A370931 Expansion of e.g.f. (1/x) * Series_Reversion( x*(1 - x*exp(x^3/6)) ).
%H A370931 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A370931 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (n-3*k)^k * (2*n-3*k)!/(6^k * k! * (n-3*k)!).
%o A370931 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(serreverse(x*(1-x*exp(x^3/6)))/x))
%o A370931 (PARI) a(n) = sum(k=0, n\3, (n-3*k)^k*(2*n-3*k)!/(6^k*k!*(n-3*k)!))/(n+1);
%Y A370931 Cf. A213644, A370930.
%Y A370931 Cf. A358265.
%K A370931 nonn
%O A370931 0,3
%A A370931 _Seiichi Manyama_, Mar 06 2024