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 A197842 #7 Feb 07 2025 16:44:04
%S A197842 3,8,7,7,2,2,1,2,0,2,5,4,9,8,5,3,3,4,2,7,1,8,5,2,0,0,5,2,4,8,3,2,9,2,
%T A197842 3,6,1,5,7,7,1,5,8,9,3,8,9,2,9,9,4,3,6,7,8,2,8,6,6,4,9,5,4,7,0,0,9,3,
%U A197842 5,0,2,5,3,4,4,9,6,5,8,5,5,1,3,2,2,1,7,3,7,2,1,6,3,0,2,6,2,8,3
%N A197842 Decimal expansion of greatest x having x^2+2x=cos(x).
%C A197842 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A197842 least x: -1.85071744156198290129787883145887449239...
%e A197842 greatest x: 0.38772212025498533427185200524832923...
%t A197842 a = 1; b = 2; c = 1;
%t A197842 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A197842 Plot[{f[x], g[x]}, {x, -2, 1}]
%t A197842 r1 = x /. FindRoot[f[x] == g[x], {x, -1.9, -1.8}, WorkingPrecision -> 110]
%t A197842 RealDigits[r1] (* A197841 *)
%t A197842 r2 = x /. FindRoot[f[x] == g[x], {x, .38, .39}, WorkingPrecision -> 110]
%t A197842 RealDigits[r2] (* A197842 *)
%Y A197842 Cf. A197737.
%K A197842 nonn,cons
%O A197842 0,1
%A A197842 _Clark Kimberling_, Oct 20 2011