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 A379867 #18 Jan 05 2025 09:58:34
%S A379867 1,2,23,529,18589,884281,53195407,3874595089,331580316473,
%T A379867 32614443047521,3625839880813171,449629404853604185,
%U A379867 61535275741655857621,9213155228282408405185,1498018121369750569371959,262869047482982449625840161,49515850496472530668242845041
%N A379867 E.g.f. A(x) satisfies A(x) = 1/(exp(-x*A(x)^2) - x*A(x)^2).
%F A379867 E.g.f.: sqrt( (1/x) * Series_Reversion( x * (exp(-x) - x)^2 ) ).
%F A379867 a(n) = n! * Sum_{k=0..n} (3*n-k+1)^(k-1) * binomial(3*n-k+1,n-k)/k!.
%o A379867 (PARI) a(n) = n!*sum(k=0, n, (3*n-k+1)^(k-1)*binomial(3*n-k+1, n-k)/k!);
%Y A379867 Cf. A377890, A379870.
%Y A379867 Cf. A377892, A379884.
%Y A379867 Cf. A377891, A377893, A379886.
%Y A379867 Cf. A364985, A379864.
%K A379867 nonn
%O A379867 0,2
%A A379867 _Seiichi Manyama_, Jan 04 2025