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 A363581 #7 Jun 10 2023 09:57:22
%S A363581 1,1,-1,4,-6,11,-22,62,-151,353,-867,2261,-5861,15178,-39878,106099,
%T A363581 -283823,763248,-2065453,5621318,-15368682,42190539,-116281176,
%U A363581 321647511,-892617214,2484583934,-6935203356,19408586888,-54447145335,153084848495
%N A363581 G.f. satisfies A(x) = exp( Sum_{k>=1} A(x^k) * x^k/(k * (1 + 3*x^k)) ).
%F A363581 A(x) = (1 + 3*x) * B(x) where B(x) is the g.f. of A363579.
%F A363581 a(n) = A363579(n) + 3*A363579(n-1) for n > 0.
%o A363581 (PARI) seq(n) = my(A=1); for(i=1, n, A=exp(sum(k=1, i, subst(A, x, x^k)*x^k/(k*(1+3*x^k)))+x*O(x^n))); Vec(A);
%Y A363581 Cf. A052855, A198518, A363545, A363546, A363580.
%Y A363581 Cf. A363579.
%K A363581 sign
%O A363581 0,4
%A A363581 _Seiichi Manyama_, Jun 10 2023