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 A199667 #8 Feb 08 2025 22:14:40
%S A199667 3,0,7,3,2,0,6,2,1,1,8,2,8,1,9,4,0,7,3,4,1,1,9,6,6,6,9,3,8,6,1,5,4,9,
%T A199667 1,9,8,2,5,4,5,0,8,1,6,4,8,4,3,3,6,2,0,7,1,8,6,5,5,8,1,5,0,8,0,0,3,9,
%U A199667 2,5,4,8,6,2,7,6,6,1,5,9,2,9,6,3,3,6,7,8,6,6,7,5,0,0,8,2,3,7,2
%N A199667 Decimal expansion of x<0 satisfying 3*x^2+2*x*cos(x)=sin(x).
%C A199667 See A199597 for a guide to related sequences. The Mathematica program includes a graph.
%H A199667 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%e A199667 -0.30732062118281940734119666938615491...
%t A199667 a = 3; b = 2; c = 1;
%t A199667 f[x_] := a*x^2 + b*x*Cos[x]; g[x_] := c*Sin[x]
%t A199667 Plot[{f[x], g[x]}, {x, -1, 1.5}, {AxesOrigin -> {0, 0}}]
%t A199667 r = x /. FindRoot[f[x] == g[x], {x, -.31, -.30}, WorkingPrecision -> 110]
%t A199667 RealDigits[r] (* A199667 *)
%Y A199667 Cf. A199597.
%K A199667 nonn,cons
%O A199667 0,1
%A A199667 _Clark Kimberling_, Nov 09 2011