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 A197839 #6 Feb 07 2025 16:44:04
%S A197839 2,5,8,3,9,2,1,4,4,3,7,1,5,9,9,6,7,4,0,2,7,5,7,4,2,3,8,0,7,3,8,6,0,2,
%T A197839 7,5,2,6,1,0,1,6,7,1,1,3,5,5,3,3,3,7,1,4,8,5,1,6,5,7,1,4,3,0,0,8,6,6,
%U A197839 0,7,0,4,4,6,0,0,0,8,7,7,8,1,4,7,0,5,5,3,8,8,8,7,4,3,7,8,8,4,2
%N A197839 Decimal expansion of least x having x^2-4x=-cos(x).
%C A197839 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A197839 least x: 0.25839214437159967402757423807386027526101...
%e A197839 greatest x: 4.13257347075386830819844170536280612105...
%t A197839 a = 1; b = -4; c = -1;
%t A197839 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A197839 Plot[{f[x], g[x]}, {x, -1, 5}]
%t A197839 r1 = x /. FindRoot[f[x] == g[x], {x, -4.2, -4.1}, WorkingPrecision -> 110]
%t A197839 RealDigits[r1] (* A197839 *)
%t A197839 r2 = x /. FindRoot[f[x] == g[x], {x, 4.1, 4.2}, WorkingPrecision -> 110]
%t A197839 RealDigits[r2] (* A197840 *)
%Y A197839 Cf. A197737.
%K A197839 nonn,cons
%O A197839 0,1
%A A197839 _Clark Kimberling_, Oct 20 2011