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 A197810 #7 Feb 07 2025 16:44:04
%S A197810 7,8,8,3,9,6,8,4,5,9,9,2,9,6,5,4,2,9,0,7,8,8,2,0,9,8,3,9,8,2,0,0,1,9,
%T A197810 1,2,2,9,5,5,1,8,7,5,3,5,3,1,2,0,4,9,1,8,6,5,0,5,6,6,5,9,8,2,7,0,6,7,
%U A197810 8,7,2,5,7,2,4,8,7,8,1,4,6,0,0,8,8,9,3,3,7,6,7,8,6,9,8,6,2,8,2
%N A197810 Decimal expansion of x>0 having x^2+x=2*cos(x).
%C A197810 See A197737 for a guide to related sequences. The Mathematica program includes a graph.
%e A197810 negative: -1.3405253081973984478676062849960660920583...
%e A197810 positive: 0.7883968459929654290788209839820019122955...
%t A197810 a = 1; b = 1; c = 2;
%t A197810 f[x_] := a*x^2 + b*x; g[x_] := c*Cos[x]
%t A197810 Plot[{f[x], g[x]}, {x, -2, 1.5}]
%t A197810 r1 = x /. FindRoot[f[x] == g[x], {x, -1.5, -1.3}, WorkingPrecision -> 110]
%t A197810 RealDigits[r1] (* A197809 *)
%t A197810 r2 = x /. FindRoot[f[x] == g[x], {x, .78, .79}, WorkingPrecision -> 110]
%t A197810 RealDigits[r2] (* A197810 *)
%Y A197810 Cf. A197737.
%K A197810 nonn,cons
%O A197810 0,1
%A A197810 _Clark Kimberling_, Oct 20 2011