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 A351057 #5 Feb 01 2022 19:57:27
%S A351057 1,1,1,7,49,349,2593,20755,184609,1851289,20735041,253471039,
%T A351057 3310505425,45630322741,660993079393,10065000586507,161262522401089,
%U A351057 2717539655666353,48053169836707969,888408313419305719,17108882037936283249,342144175940842590349,7089944927940141776545
%N A351057 G.f. A(x) satisfies: A(x) = 1 + x + x^2 * A(x/(1 - 6*x)) / (1 - 6*x).
%C A351057 Shifts 2 places left under 6th-order binomial transform.
%F A351057 a(0) = a(1) = 1; a(n) = Sum_{k=0..n-2} binomial(n-2,k) * 6^k * a(n-k-2).
%t A351057 nmax = 22; A[_] = 0; Do[A[x_] = 1 + x + x^2 A[x/(1 - 6 x)]/(1 - 6 x) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%t A351057 a[0] = a[1] = 1; a[n_] := a[n] = Sum[Binomial[n - 2, k] 6^k a[n - k - 2], {k, 0, n - 2}]; Table[a[n], {n, 0, 22}]
%Y A351057 Cf. A005012, A007472, A007476, A351049, A351050, A351056.
%K A351057 nonn
%O A351057 0,4
%A A351057 _Ilya Gutkovskiy_, Jan 30 2022