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 A198128 #6 Feb 07 2025 16:44:04
%S A198128 2,7,1,8,3,1,8,5,1,8,9,5,8,0,5,9,0,7,1,8,6,8,8,2,0,3,3,3,5,8,8,3,9,7,
%T A198128 6,2,7,5,0,2,0,4,9,6,5,7,2,7,6,0,5,9,5,0,8,2,5,3,0,1,4,3,8,9,5,8,6,4,
%U A198128 8,6,0,0,8,2,1,5,1,5,5,6,7,9,0,9,3,5,2,1,7,2,9,6,5,7,5,2,0,5,4
%N A198128 Decimal expansion of least x having 2*x^2+3x=cos(x).
%C A198128 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A198128 least x: -1.51753898066148224483274698639081150...
%e A198128 greatest x: 0.2718318518958059071868820333588397...
%t A198128 a = 2; b = 3; c = 1;
%t A198128 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A198128 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A198128 r1 = x /. FindRoot[f[x] == g[x], {x, -1.52, -1.51}, WorkingPrecision -> 110]
%t A198128 RealDigits[r1](* A198128 *)
%t A198128 r2 = x /. FindRoot[f[x] == g[x], {x, .27, .28}, WorkingPrecision -> 110]
%t A198128 RealDigits[r2](* A198129 *)
%Y A198128 Cf. A197737.
%K A198128 nonn,cons
%O A198128 1,1
%A A198128 _Clark Kimberling_, Oct 22 2011