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 A198239 #6 Feb 07 2025 16:44:05
%S A198239 3,6,6,2,4,0,8,1,5,6,6,0,4,6,3,7,1,8,3,8,4,1,5,8,1,8,8,6,9,7,6,4,4,4,
%T A198239 0,5,4,7,4,3,1,6,0,8,8,4,0,0,7,0,5,9,1,1,9,3,7,7,4,4,5,1,4,1,3,6,4,9,
%U A198239 0,2,2,0,6,8,1,8,3,5,2,1,5,9,0,0,0,7,9,7,9,3,0,3,4,1,8,4,5,4,4
%N A198239 Decimal expansion of greatest x having 3*x^2+4x=2*cos(x).
%C A198239 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198239 least x: -1.40936392163577784477286936880153979511...
%e A198239 greatest x: 0.36624081566046371838415818869764440...
%t A198239 a = 3; b = 4; c = 2;
%t A198239 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198239 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A198239 r1 = x /. FindRoot[f[x] == g[x], {x, -1.5, -1.4}, WorkingPrecision -> 110]
%t A198239 RealDigits[r1](* A198238 *)
%t A198239 r2 = x /. FindRoot[f[x] == g[x], {x, .36, .37}, WorkingPrecision -> 110]
%t A198239 RealDigits[r2](* A198239 *)
%Y A198239 Cf. A197737.
%K A198239 nonn,cons
%O A198239 0,1
%A A198239 _Clark Kimberling_, Oct 23 2011