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 A198350 #6 Feb 07 2025 16:44:05
%S A198350 3,7,3,3,9,5,9,1,6,0,1,9,3,9,6,9,6,8,8,9,6,8,3,2,1,5,1,9,8,1,8,4,7,6,
%T A198350 3,1,5,9,9,6,4,4,5,8,2,7,2,7,2,9,8,8,8,9,5,4,7,1,5,6,2,9,0,9,6,4,5,2,
%U A198350 5,2,1,1,0,8,3,2,2,5,5,5,8,6,0,2,5,0,1,6,0,5,3,7,6,8,6,3,6,4,2
%N A198350 Decimal expansion of greatest x having 4*x^2+x=cos(x).
%C A198350 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198350 least x: -0.596628694828122209772071553484966...
%e A198350 greatest x: 0.3733959160193969688968321519818...
%t A198350 a = 4; b = 1; c = 1;
%t A198350 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198350 Plot[{f[x], g[x]}, {x, -1, 1}]
%t A198350 r1 = x /. FindRoot[f[x] == g[x], {x, -.6, -.5}, WorkingPrecision -> 110]
%t A198350 RealDigits[r1] (* A198349 *)
%t A198350 r2 = x /. FindRoot[f[x] == g[x], {x, .37, .38}, WorkingPrecision -> 110]
%t A198350 RealDigits[r2] (* A198350 *)
%Y A198350 Cf. A197737.
%K A198350 nonn,cons
%O A198350 0,1
%A A198350 _Clark Kimberling_, Oct 23 2011