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 A379847 #13 Feb 05 2025 09:22:31
%S A379847 1,2,17,259,5773,171021,6342937,283094309,14785425081,885090944809,
%T A379847 59765476266061,4494836808752049,372655043070926821,
%U A379847 33769844474642217293,3320996349535681398849,352267766021524028011981,40091829710459334010532593,4873329774181782935197522641
%N A379847 Expansion of e.g.f. (1/x) * Series_Reversion( x * exp(-x) / (1 + x*exp(3*x)) ).
%F A379847 a(n) = (n!/(n+1)) * Sum_{k=0..n} (4*n-3*k+1)^k * binomial(n+1,n-k)/k!.
%F A379847 E.g.f. A(x) satisfies A(x) = exp(x*A(x)) / ( 1 - x*exp(4*x*A(x)) ). - _Seiichi Manyama_, Feb 04 2025
%o A379847 (PARI) a(n) = n!*sum(k=0, n, (4*n-3*k+1)^k*binomial(n+1, n-k)/k!)/(n+1);
%Y A379847 Cf. A088690, A379456, A379846.
%Y A379847 Cf. A366233, A379702.
%K A379847 nonn
%O A379847 0,2
%A A379847 _Seiichi Manyama_, Jan 04 2025