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 A180400 #19 Mar 27 2023 10:14:32
%S A180400 1,3,21,162,1341,11529,101619,911466,8281737,76002381,703017549,
%T A180400 6544803564,61254970686,575885086182,5434948357146,51462813578148,
%U A180400 488705091057981,4652700300002475,44395945025504625,424479488258350350
%N A180400 Coefficients of Maclaurin series for (1-9x-9x^2)^(-1/3).
%H A180400 Vincenzo Librandi, <a href="/A180400/b180400.txt">Table of n, a(n) for n = 0..200</a>
%F A180400 G.f.: (1-9x-9x^2)^(-1/3).
%F A180400 D-finite with recurrence: n*a(n) = 3*(3*n-2)*a(n-1) + 3*(3*n-4)*a(n-2). - _Vaclav Kotesovec_, Oct 20 2012
%F A180400 a(n) ~ sqrt(3)*Gamma(2/3)/(2^(2/3)*(13-3*sqrt(13))^(1/3)*Pi) * ((9+3*sqrt(13))/2)^n/(n^(2/3)). - _Vaclav Kotesovec_, Oct 20 2012
%F A180400 a(n) = Sum_{k=0..n} (-9)^k * binomial(-1/3,k) * binomial(k,n-k). - _Seiichi Manyama_, Mar 27 2023
%e A180400 The Maclaurin series begins with 1 + 3x + 21x^2.
%t A180400 CoefficientList[Series[Power[1-9x-9x^2, (-3)^-1],{x,0,20}],x] (* _Harvey P. Dale_, Mar 11 2012 *)
%Y A180400 Cf. A180399.
%K A180400 nonn,easy
%O A180400 0,2
%A A180400 _Clark Kimberling_, Sep 01 2010, Sep 02 2010