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 A198358 #6 Feb 07 2025 16:44:05
%S A198358 2,9,9,0,0,5,8,7,4,5,5,0,3,1,7,3,5,7,0,3,7,4,6,8,3,5,0,7,2,4,5,4,1,9,
%T A198358 3,9,3,2,7,5,7,6,1,9,1,7,0,1,7,3,6,6,4,0,3,0,6,4,6,5,8,6,5,0,6,8,3,1,
%U A198358 7,8,6,7,7,0,8,4,2,8,0,2,3,5,9,0,7,3,6,2,5,6,6,1,7,4,9,4,8,2,2
%N A198358 Decimal expansion of greatest x having 4*x^2+2x=cos(x).
%C A198358 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198358 least x: -0.7460743621285644617325741898565306735...
%e A198358 greatest x: 0.29900587455031735703746835072454193932...
%t A198358 a = 4; b = 2; c = 1;
%t A198358 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198358 Plot[{f[x], g[x]}, {x, -1, 1}]
%t A198358 r1 = x /. FindRoot[f[x] == g[x], {x, -.8, -.7}, WorkingPrecision -> 110]
%t A198358 RealDigits[r1] (* A198357 *)
%t A198358 r2 = x /. FindRoot[f[x] == g[x], {x, .29, .30}, WorkingPrecision -> 110]
%t A198358 RealDigits[r2] (* A198358 *)
%Y A198358 Cf. A197737.
%K A198358 nonn,cons
%O A198358 0,1
%A A198358 _Clark Kimberling_, Oct 24 2011