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 A199447 #8 Feb 08 2025 09:19:01
%S A199447 6,3,8,8,9,0,3,0,3,9,5,0,9,5,0,8,0,9,1,6,4,7,9,2,9,1,3,6,6,3,0,6,3,4,
%T A199447 3,6,9,0,5,9,3,9,2,3,0,0,6,9,9,8,6,1,7,0,6,8,2,8,4,0,4,4,3,9,0,8,5,1,
%U A199447 5,8,5,4,8,0,4,3,6,7,2,4,3,8,6,4,8,3,1,5,1,4,6,7,8,6,7,0,5,5,0
%N A199447 Decimal expansion of x>0 satisfying 3*x^2+x*sin(x)=2*cos(x).
%C A199447 See A199370 for a guide to related sequences. The Mathematica program includes a graph.
%H A199447 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%e A199447 0.6388903039509508091647929136630634369059392300...
%t A199447 a = 3; b = 1; c = 2;
%t A199447 f[x_] := a*x^2 + b*x*Sin[x]; g[x_] := c*Cos[x]
%t A199447 Plot[{f[x], g[x]}, {x, -Pi, Pi}, {AxesOrigin -> {0, 0}}]
%t A199447 r = x /. FindRoot[f[x] == g[x], {x, .63, .64}, WorkingPrecision -> 110]
%t A199447 RealDigits[r] (* A199447 *)
%Y A199447 Cf. A199429.
%K A199447 nonn,cons
%O A199447 0,1
%A A199447 _Clark Kimberling_, Nov 06 2011