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 A197821 #13 Aug 15 2021 14:50:56
%S A197821 4,5,9,2,9,5,3,4,1,2,6,2,1,0,7,5,5,1,0,5,4,8,3,7,5,1,0,3,5,8,0,5,2,6,
%T A197821 4,9,1,9,2,0,0,4,0,4,2,1,4,7,2,5,5,0,7,2,7,3,4,0,9,2,9,0,5,4,5,3,3,6,
%U A197821 9,0,1,8,8,4,9,5,0,8,0,6,9,5,5,7,2,6,2,8,7,5,9,9,6,1,8,6,1,5,9
%N A197821 Decimal expansion of least x > 0 having sin(2*x) = Pi*sin(2*Pi*x).
%C A197821 For a discussion and guide to related sequences, see A197739.
%e A197821 0.45929534126210755105483751035805264919200...
%t A197821 b = 1; c = Pi;
%t A197821 f[x_] := Cos[b*x]^2; g[x_] := Sin[c*x]^2; s[x_] := f[x] + g[x];
%t A197821 r = x /. FindRoot[b*Sin[2 b*x] == c*Sin[2 c*x], {x, .45, .46}, WorkingPrecision -> 110]
%t A197821 RealDigits[r] (* A197821 *)
%t A197821 m = s[r]
%t A197821 RealDigits[m] (* A197822 *)
%t A197821 Plot[{b*Sin[2 b*x], c*Sin[2 c*x]}, {x, 0, Pi}]
%t A197821 d = m/2; t = x /. FindRoot[s[x] == d, {x, .7, .8}, WorkingPrecision -> 110]
%t A197821 RealDigits[t] (* A197823 *)
%t A197821 Plot[{s[x], d}, {x, 0, Pi}, AxesOrigin -> {0, 0}]
%t A197821 d = m/3; t = x /. FindRoot[s[x] == d, {x, .8, .9}, WorkingPrecision -> 110]
%t A197821 RealDigits[t] (* A197824 *)
%t A197821 Plot[{s[x], d}, {x, 0, Pi}, AxesOrigin -> {0, 0}]
%t A197821 d = 1; t = x /. FindRoot[s[x] == d, {x, .7, .8}, WorkingPrecision -> 110]
%t A197821 RealDigits[t] (* A197726 *)
%t A197821 Plot[{s[x], d}, {x, 0, Pi}, AxesOrigin -> {0, 0}]
%t A197821 d = 1/2; t = x /. FindRoot[s[x] == d, {x, .89, 9.1}, WorkingPrecision -> 110]
%t A197821 RealDigits[t] (* A197826 *)
%t A197821 Plot[{s[x], d}, {x, 0, Pi}, AxesOrigin -> {0, 0}]
%Y A197821 Cf. A197739.
%K A197821 nonn,cons
%O A197821 0,1
%A A197821 _Clark Kimberling_, Oct 19 2011
%E A197821 Definition corrected by _Georg Fischer_, Aug 10 2021