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 A198221 #6 Feb 07 2025 16:44:05
%S A198221 8,0,7,6,7,8,4,8,2,4,2,7,2,1,0,6,5,0,9,1,8,0,5,7,2,1,3,0,7,8,3,7,5,6,
%T A198221 6,3,5,0,3,8,6,6,3,6,1,6,6,1,1,3,0,6,4,0,9,0,6,6,7,9,8,0,4,1,2,7,9,3,
%U A198221 8,4,5,9,3,1,7,3,4,2,5,1,7,7,5,5,3,8,9,7,0,5,9,1,5,1,4,1,2,1,4
%N A198221 Decimal expansion of greatest x having 3*x^2+x=4*cos(x).
%C A198221 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198221 least x: -1.0190925028154180679841791260898590369...
%e A198221 greatest x: 0.807678482427210650918057213078375663...
%t A198221 a = 3; b = 1; c = 4;
%t A198221 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198221 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A198221 r1 = x /. FindRoot[f[x] == g[x], {x, -1.1, -1}, WorkingPrecision -> 110]
%t A198221 RealDigits[r1] (* A198220 *)
%t A198221 r2 = x /. FindRoot[f[x] == g[x], {x, .8, .9}, WorkingPrecision -> 110]
%t A198221 RealDigits[r2] (* A198221 *)
%Y A198221 Cf. A197737.
%K A198221 nonn,cons
%O A198221 0,1
%A A198221 _Clark Kimberling_, Oct 22 2011