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 A198231 #7 Feb 07 2025 16:44:05
%S A198231 2,5,6,5,8,4,9,3,4,2,2,3,5,6,9,4,4,0,1,5,0,4,5,7,9,4,7,4,9,9,0,9,3,5,
%T A198231 5,9,7,4,9,3,1,3,4,1,1,9,4,6,0,6,7,2,9,3,7,2,5,2,0,1,7,4,8,4,7,5,7,2,
%U A198231 0,4,3,3,0,3,2,9,1,8,9,9,0,1,8,4,9,6,1,4,3,3,4,1,3,0,9,1,2,6,9
%N A198231 Decimal expansion of greatest x having 3*x^2+3x=cos(x).
%C A198231 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198231 least x: -1.1269965961113996583452373843254048549...
%e A198231 greatest x: 0.25658493422356944015045794749909355...
%t A198231 a = 3; b = 3; c = 1;
%t A198231 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198231 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A198231 r1 = x /. FindRoot[f[x] == g[x], {x, -1.2, -1.1}, WorkingPrecision -> 110]
%t A198231 RealDigits[r1] (* A198230 *)
%t A198231 r2 = x /. FindRoot[f[x] == g[x], {x, .25, .26}, WorkingPrecision -> 110]
%t A198231 RealDigits[r2] (* A198231 *)
%Y A198231 Cf. A197737.
%K A198231 nonn,cons
%O A198231 0,1
%A A198231 _Clark Kimberling_, Oct 23 2011