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 A103546 #19 Feb 16 2025 08:32:56
%S A103546 2,4,8,6,3,4,3,7,6,4,9,5,9,0,7,9,6,6,5,2,6,7,1,9,5,3,3,0,9,7,0,7,2,2,
%T A103546 1,2,0,1,4,0,9,0,3,8,5,2,5,9,2,7,0,5,8,1,9,7,6,4,9,9,4,0,3,3,2,9,9,1,
%U A103546 1,1,8,5,4,0,0,1,1,4,7,3,0,5,5,1,5,5,9,0,9,1,0,4,6,9,2,8,0,8,0,1,7,2,3,1,7
%N A103546 Decimal expansion of the negated value of the smallest real root of the quintic equation x^5 + 2*x^4 - 2*x^3 - x^2 + 2*x -1 = 0.
%C A103546 This is an approximation to the Feigenbaum reduction parameter.
%C A103546 The other two real roots are 0.76660865407289... and -1.16317291980104...
%H A103546 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FeigenbaumConstant.html">Feigenbaum Constant</a>.
%H A103546 <a href="/index/Al#algebraic_05">Index entries for algebraic numbers, degree 5</a>
%e A103546 The real roots are (roughly) -2.486343765, -1.163172920, 0.7666086541.
%t A103546 RealDigits[ FindRoot[x^5 + 2x^4 - 2x^3 - x^2 + 2x - 1 == 0, {x, -3}, WorkingPrecision -> 2^7][[1, 2]]][[1]] (* _Robert G. Wilson v_, Mar 26 2005 *)
%t A103546 Root[#^5 + 2#^4 - 2#^3 - #^2 + 2# - 1&, 1] // RealDigits[#, 10, 105]& // First (* _Jean-François Alcover_, Feb 27 2013 *)
%o A103546 (PARI) polrootsreal(x^5 - 2*x^4 - 2*x^3 + x^2 + 2*x + 1)[3] \\ _Charles R Greathouse IV_, Apr 14 2014
%Y A103546 Cf. A006891, A103616.
%K A103546 cons,nonn
%O A103546 1,1
%A A103546 Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 23 2005