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