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 A348858 #7 Nov 02 2021 09:50:06
%S A348858 1,2,9,103,3101,261192,64285189,47059492688,103060910397021,
%T A348858 676492249628112382,13317427360663454672669,
%U A348858 786420726604930579016189223,139314431838014895142151741877241,74037818920801629179455290512454633872,118040419689979917511971388549088825283510249
%N A348858 G.f. A(x) satisfies: A(x) = 1 / ((1 - x) * (1 - x * A(3*x))).
%F A348858 a(n) = 1 + Sum_{k=0..n-1} 3^k * a(k) * a(n-k-1).
%F A348858 a(n) ~ c * 3^(n*(n-1)/2), where c = 4.508135635010167805309616576501854361005320931661829410476785686203732753... - _Vaclav Kotesovec_, Nov 02 2021
%t A348858 nmax = 14; A[_] = 0; Do[A[x_] = 1/((1 - x) (1 - x A[3 x])) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%t A348858 a[n_] := a[n] = 1 + Sum[3^k a[k] a[n - k - 1], {k, 0, n - 1}]; Table[a[n], {n, 0, 14}]
%Y A348858 Cf. A007317, A015084, A348857, A348859.
%K A348858 nonn
%O A348858 0,2
%A A348858 _Ilya Gutkovskiy_, Nov 02 2021