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 A379662 #8 Dec 29 2024 08:48:58
%S A379662 1,4,55,1407,53697,2743893,176247927,13657260501,1240444335969,
%T A379662 129281173193385,15210977483374479,1994549350608453609,
%U A379662 288445997202717914433,45611213861740547292093,7829287622920723803498279,1449907335654700964735333997,288151338120152032299063196737
%N A379662 Expansion of e.g.f. (1/x) * Series_Reversion( x * (exp(-3*x) - x) ).
%F A379662 a(n) = n! * Sum_{k=0..n} 3^k * (2*n-k+1)^(k-1) * binomial(2*n-k+1,n-k)/k!.
%o A379662 (PARI) a(n) = n!*sum(k=0, n, 3^k*(2*n-k+1)^(k-1)*binomial(2*n-k+1, n-k)/k!);
%Y A379662 Cf. A377890, A379661.
%K A379662 nonn
%O A379662 0,2
%A A379662 _Seiichi Manyama_, Dec 29 2024