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 A199781 #8 Feb 08 2025 22:32:34
%S A199781 1,3,9,8,8,0,6,8,9,3,8,9,4,9,0,3,2,5,9,7,9,1,2,3,8,1,1,8,9,8,3,7,9,1,
%T A199781 3,8,4,0,2,8,5,1,9,8,5,7,0,6,5,0,4,7,1,7,1,7,2,5,2,4,0,7,5,2,9,7,8,9,
%U A199781 2,2,8,5,1,5,2,4,5,5,8,2,5,5,9,1,7,2,4,8,0,9,4,0,3,7,0,1,1,8,0
%N A199781 Decimal expansion of x>0 satisfying 2*x^2-4*x*cos(x)=3*sin(x).
%C A199781 See A199597 for a guide to related sequences. The Mathematica program includes a graph.
%H A199781 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%e A199781 1.3988068938949032597912381189837913840285...
%t A199781 a = 2; b = -4; c = 3;
%t A199781 f[x_] := a*x^2 + b*x*Cos[x]; g[x_] := c*Sin[x]
%t A199781 Plot[{f[x], g[x]}, {x, -1, 2}, {AxesOrigin -> {0, 0}}]
%t A199781 r = x /. FindRoot[f[x] == g[x], {x, 1.39, 1.40}, WorkingPrecision -> 110]
%t A199781 RealDigits[r] (* A199781 *)
%Y A199781 Cf. A199597.
%K A199781 nonn,cons
%O A199781 1,2
%A A199781 _Clark Kimberling_, Nov 10 2011