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 A337570 #35 Oct 27 2023 11:58:12
%S A337570 1,2,8,3,7,8,1,6,6,5,8,6,3,5,3,8,2,0,8,3,0,5,2,6,4,3,2,9,5,7,0,4,7,2,
%T A337570 1,5,0,8,7,6,4,6,2,8,1,6,2,3,9,7,0,2,0,1,2,9,7,2,8,5,7,3,2,9,8,7,9,3,
%U A337570 6,0,5,0,2,4,0,2,3,7,4,2,7,6,1,7,1,8,4,7,8,3,5,8,0,1,2,2,9
%N A337570 Decimal expansion of the real positive solution to x^4 = 4-x.
%C A337570 x = (4 - (4 - (4 - ... )^(1/4))^(1/4))^(1/4).
%C A337570 The negative value (-1.2837816658...) is the real negative solution to x^4 = x+4.
%H A337570 <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>
%F A337570 Equals sqrt(sqrt(1/s) - s/16) - sqrt(s/16) where s = (sqrt(16804864/27) + 32)^(1/3) - (sqrt(16804864/27) - 32)^(1/3). [Simplified by _Michal Paulovic_, Jun 22 2021]
%e A337570 1.28378166586...
%t A337570 RealDigits[x /. FindRoot[x^4 + x - 4, {x, 1}, WorkingPrecision -> 100], 10, 90][[1]] (* _Amiram Eldar_, Sep 03 2020 *)
%o A337570 (PARI) solve(n=0,2,n^4+n-4)
%o A337570 (PARI) polroots(n^4+n-4)[2]
%o A337570 (PARI) polrootsreal(x^4+x-4)[2] \\ _Charles R Greathouse IV_, Oct 27 2023
%o A337570 (MATLAB) format long; solve('x^4+x-4=0'); ans(3), (eval(ans))
%Y A337570 Cf. A337571.
%K A337570 nonn,cons
%O A337570 1,2
%A A337570 _Michal Paulovic_, Sep 01 2020