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 A328824 #38 Nov 13 2023 04:52:50
%S A328824 0,1,1,1,-7,-7,-7,57,57,57,-455,-455,-455,3641,3641,3641,-29127,
%T A328824 -29127,-29127,233017,233017,233017,-1864135,-1864135,-1864135,
%U A328824 14913081,14913081,14913081,-119304647,-119304647,-119304647
%N A328824 Numerators of A113405(-n) (see the comment for details).
%C A328824 Let A(n) = (2^n + (-1)^(n+1) - 2*sqrt(3)*sin((Pi*n)/3))/9. Then A(n) = A113405(n) and a(n) = numerator(A(-n)).
%H A328824 Colin Barker, <a href="/A328824/b328824.txt">Table of n, a(n) for n = 0..1000</a>
%H A328824 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-8,8).
%F A328824 From _Colin Barker_, Nov 11 2019: (Start)
%F A328824 G.f.: x / ((1 - x)*(1 + 2*x)*(1 - 2*x + 4*x^2)).
%F A328824 a(n) = a(n-1) - 8*a(n-3) + 8*a(n-4) for n>3. (End)
%p A328824 gf := x / ((1 - x)*(1 + 2*x)*(1 - 2*x + 4*x^2)): ser := series(gf, x, 36):
%p A328824 seq(coeff(ser,x,n),n=0..30); # _Peter Luschny_, Nov 11 2019
%t A328824 LinearRecurrence[{1,0,-8,8},{0,1,1,1},50] (* _Paolo Xausa_, Nov 13 2023 *)
%o A328824 (PARI) concat(0, Vec(x / ((1 - x)*(1 + 2*x)*(1 - 2*x + 4*x^2)) + O(x^40))) \\ _Colin Barker_, Nov 11 2019
%Y A328824 Cf. A000079, A014990, A015565, A113405, A139818.
%K A328824 sign,easy,frac
%O A328824 0,5
%A A328824 _Paul Curtz_, Oct 28 2019