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 A179489 #11 Jun 04 2021 23:23:04
%S A179489 1,1,2,8,44,288,2172,18516,175352,1819868,20491844,248417128,
%T A179489 3221797252,44464876996,650076797232,10028658649668,162695157490644,
%U A179489 2767333692834768,49221196196394252,913310582666986596
%N A179489 G.f.: A(x) = x/(1 - (1-3x)*A( x/(1-3x) )).
%F A179489 G.f.: A(x) = x/(1 - (1-3x)*x/(1-3x - (1-6x)*x/(1-6x - (1-9x)*x/(1-9x - (1-12x)*x/(1-12x - ... (continued fraction).
%F A179489 From _Gary W. Adamson_, Jul 22 2011: (Start)
%F A179489 a(n) = the upper left term in M^(n-1), M = an infinite square production matrix with the series 3*n-2 as the main diagonal:
%F A179489 1, 1, 0, 0, 0, ...
%F A179489 1, 4, 1, 0, 0, ...
%F A179489 1, 1, 7, 1, 0, ...
%F A179489 1, 1, 1,10, 0, ...
%F A179489 ... (End)
%e A179489 G.f.: A(x) = x + x^2 + 2*x^3 + 8*x^4 + 44*x^5 + 288*x^6 + ...
%e A179489 A(x) = x + x*A(x) + x*A(x)*A(x/(1-3x)) + x*A(x)*A(x/(1-3x))*A(x/(1-6x)) + x*A(x)*A(x/(1-3x))*A(x/(1-6x))*A(x/(1-9x)) +...
%o A179489 (PARI) {a(n)=local(A=x+x^2);for(i=1,n,A=x/(1-(1-3*x)*subst(A,x,x/(1-3*x+x^2*O(x^n)))));polcoeff(A,n)}
%Y A179489 Cf. variants: A074664, A179488.
%K A179489 nonn
%O A179489 1,3
%A A179489 _Paul D. Hanna_, Aug 13 2010