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 A197520 #7 Feb 16 2025 05:30:25
%S A197520 9,0,6,3,6,2,2,3,6,5,3,8,7,2,1,4,1,7,5,1,9,6,9,1,9,2,2,7,5,8,8,4,6,9,
%T A197520 1,0,3,1,2,0,8,8,7,1,0,3,0,1,9,2,0,1,8,0,4,1,4,4,0,8,9,3,8,8,7,3,7,2,
%U A197520 3,9,2,8,6,2,0,8,5,9,6,8,1,5,6,0,8,2,0,2,8,8,5,2,4,6,7,6,1,3,4
%N A197520 Decimal expansion of least x>0 having cos(2*Pi*x)=(cos 3x)^2.
%C A197520 The Mathematica program includes a graph. See A197476 for a guide for the least x>0 satisfying cos(b*x)=(cos(c*x))^2 for selected b and c.
%C A197520 This number is irrational. I cannot prove it to be algebraic or transcendental. - _Charles R Greathouse IV_, Feb 16 2025
%e A197520 0.9063622365387214175196919227588469103120887...
%t A197520 b = 2 Pi; c = 3; f[x_] := Cos[x]
%t A197520 t = x /. FindRoot[f[b*x] == f[c*x]^2, {x, .9, .91}, WorkingPrecision -> 200]
%t A197520 RealDigits[t] (* A197520 *)
%t A197520 Plot[{f[b*x], f[c*x]^2}, {x, 0, Pi/2}]
%Y A197520 Cf. A197476.
%K A197520 nonn,cons
%O A197520 0,1
%A A197520 _Clark Kimberling_, Oct 16 2011