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 A198991 #14 Feb 07 2025 19:42:03
%S A198991 4,4,7,9,5,8,3,0,7,6,4,7,4,0,6,8,7,2,3,0,9,7,6,4,1,8,4,0,4,5,1,8,5,4,
%T A198991 0,2,3,5,3,8,9,7,5,3,4,8,4,0,6,5,7,1,0,0,2,3,4,2,3,1,3,8,3,0,3,0,3,7,
%U A198991 2,8,4,0,6,0,4,2,6,0,1,4,5,3,0,7,9,0,7,1,7,8,0,9,7,8,3,7,1,4,8
%N A198991 Decimal expansion of x>0 satisfying 4*x^2-2*cos(x)=-1.
%C A198991 See A198755 for a guide to related sequences. The Mathematica program includes a graph.
%H A198991 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%e A198991 0.44795830764740687230976418404518540235389753...
%p A198991 Digits:=100: fsolve(4*x^2-2*cos(x)=-1,x); # _Wesley Ivan Hurt_, Feb 09 2017
%t A198991 a = 4; b = -2; c = -1;
%t A198991 f[x_] := a*x^2 + b*Cos[x]; g[x_] := c
%t A198991 Plot[{f[x], g[x]}, {x, -2, 2}, {AxesOrigin -> {0, 0}}]
%t A198991 r = x /. FindRoot[f[x] == g[x], {x, .44, .45}, WorkingPrecision -> 110]
%t A198991 RealDigits[r] (* A198991 *)
%o A198991 (PARI) solve(x=0, 1, 4*x^2 - 2*cos(x) + 1) \\ _Michel Marcus_, Feb 09 2017
%Y A198991 Cf. A198755.
%K A198991 nonn,cons
%O A198991 0,1
%A A198991 _Clark Kimberling_, Nov 01 2011