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 A198138 #6 Feb 07 2025 16:44:05
%S A198138 1,4,4,7,0,5,7,1,5,1,0,4,1,6,5,5,0,7,8,7,7,9,4,7,1,6,8,1,4,4,9,8,8,0,
%T A198138 6,2,7,5,0,5,7,7,2,9,3,2,5,5,0,6,3,6,8,9,6,4,8,9,5,3,3,6,2,9,5,4,9,4,
%U A198138 1,3,3,4,8,1,0,8,7,4,9,3,3,3,4,4,2,9,6,6,7,5,8,2,5,8,1,5,7,7,9
%N A198138 Decimal expansion of least x having 3*x^2+4x=4*cos(x).
%C A198138 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198138 least x: -1.447057151041655078779471681449880627...
%e A198138 greatest x: 0.5817200797316597228428659232714882...
%t A198138 a = 3; b = 4; c = 4;
%t A198138 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198138 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A198138 r1 = x /. FindRoot[f[x] == g[x], {x, -1.5, -1.4}, WorkingPrecision -> 110]
%t A198138 RealDigits[r1] (* A198138 *)
%t A198138 r2 = x /. FindRoot[f[x] == g[x], {x, .58, .59}, WorkingPrecision -> 110]
%t A198138 RealDigits[r2] (* A198139 *)
%Y A198138 Cf. A197737.
%K A198138 nonn,cons
%O A198138 1,2
%A A198138 _Clark Kimberling_, Oct 23 2011