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 A197820 #7 Feb 07 2025 16:44:04
%S A197820 2,2,8,7,0,8,6,1,7,7,6,5,6,5,8,4,4,8,5,3,3,7,0,3,3,3,1,2,3,1,4,4,9,1,
%T A197820 7,3,7,3,9,5,7,8,2,0,7,5,1,2,9,2,3,9,8,4,0,8,2,9,0,8,4,3,9,0,0,4,0,1,
%U A197820 4,3,0,8,6,4,7,9,6,9,0,1,9,2,9,0,5,6,0,3,8,9,1,5,4,1,4,4,7,3,8
%N A197820 Decimal expansion of greatest x having x^2-2x=-cos(x).
%C A197820 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A197820 least x: 0.589303208159012874725223919073869185889...
%e A197820 greatest x: 2.287086177656584485337033312314491737...
%t A197820 a = 1; b = -2; c = -1;
%t A197820 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A197820 Plot[{f[x], g[x]}, {x, -1, 3}]
%t A197820 r1 = x /. FindRoot[f[x] == g[x], {x, .5, .6}, WorkingPrecision -> 110]
%t A197820 RealDigits[r1] (* A197815 *)
%t A197820 r2 = x /. FindRoot[f[x] == g[x], {x, 2.2, 2.3}, WorkingPrecision -> 110]
%t A197820 RealDigits[r2] (* A197820 *)
%Y A197820 Cf. A197737.
%K A197820 nonn,cons
%O A197820 1,1
%A A197820 _Clark Kimberling_, Oct 20 2011