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 A173115 #14 Mar 02 2022 13:24:48
%S A173115 0,24,2400,235224,23049600,2258625624,221322261600,21687323011224,
%T A173115 2125136332838400,208241673295152024,20405558846592060000,
%U A173115 1999536525292726728024,195934173919840627286400
%N A173115 a(n) = -(sin(2*n*arccos(sqrt(3))))^2.
%H A173115 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (99,-99,1)
%F A173115 a(n) = 99*a(n-1) - 99*a(n-2) + a(n-3), n > 2.
%F A173115 Binet formula: a(n) = -1/2 + (1/4)(49 + 20*sqrt(6))^n + (1/4)(49 - 20*sqrt(6))^n.
%F A173115 a(n) = 24*A108741(n).
%F A173115 From _R. J. Mathar_, Aug 23 2012: (Start)
%F A173115 G.f.: -24*x*(1+x) / ( (x-1)*(x^2-98*x+1) ).
%F A173115 a(n) = A132596(2n). (End)
%t A173115 Table[ -Round[N[Sin[2 n ArcCos[Sqrt[3]]]^2, 100]], {n, 0, 20}]
%t A173115 OR
%t A173115 Table[Round[N[ -1/2 + (1/4) (49 + 20 Sqrt[6])^n + (1/4) (49 - 20 Sqrt[6])^n]], {n, 0, 6}]
%t A173115 OR
%t A173115 Clear[a]; a[n_] := a[n] = 99 a[n - 1] - 99 a[n - 2] + a[n - 3]; a[0] = 0; a[1] = 24; a[2] = 2400; Table[a[n], {n, 0, 10}]
%o A173115 (PARI) a(n)=([0,1,0;0,0,1;1,-99,99]^n*[0;24;2400])[1,1] \\ _Charles R Greathouse IV_, Jun 11 2015
%Y A173115 Cf. A001079, A108741, A132592, A146311, A146312, A146313.
%K A173115 nonn,easy
%O A173115 0,2
%A A173115 _Artur Jasinski_, Feb 10 2010