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 A199271 #8 Feb 07 2025 16:44:05
%S A199271 1,3,4,2,9,0,5,1,2,2,3,2,9,3,5,6,1,5,7,7,9,5,6,2,9,2,5,8,3,8,2,8,2,5,
%T A199271 8,2,5,1,7,0,3,3,5,1,8,8,6,9,9,2,5,8,8,4,3,2,8,6,4,6,8,6,8,3,2,9,8,0,
%U A199271 6,6,7,4,7,5,6,5,6,3,3,0,0,9,2,1,8,5,3,7,1,2,7,1,9,2,1,4,9,8,1
%N A199271 Decimal expansion of x<0 satisfying 2*x^2+2*x*cos(x)=3.
%C A199271 See A199170 for a guide to related sequences. The Mathematica program includes a graph.
%H A199271 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%e A199271 negative: -1.342905122329356157795629258382825825170...
%e A199271 positive: 0.976312273615130123076470141335091567967...
%t A199271 a = 2; b = 2; c = 3;
%t A199271 f[x_] := a*x^2 + b*x*Cos[x]; g[x_] := c
%t A199271 Plot[{f[x], g[x]}, {x, -3, 3}, {AxesOrigin -> {0, 0}}]
%t A199271 r = x /. FindRoot[f[x] == g[x], {x, -1.35, -1.34}, WorkingPrecision -> 110]
%t A199271 RealDigits[r] (* A199271 *)
%t A199271 r = x /. FindRoot[f[x] == g[x], {x, .97, .98}, WorkingPrecision -> 110]
%t A199271 RealDigits[r] (* A199272 *)
%Y A199271 Cf. A199170.
%K A199271 nonn,cons
%O A199271 1,2
%A A199271 _Clark Kimberling_, Nov 04 2011