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 A202540 #11 May 14 2019 23:54:54
%S A202540 1,9,9,4,6,0,5,7,8,2,4,3,0,0,5,3,5,1,4,8,8,5,7,7,7,1,8,3,8,4,9,4,9,1,
%T A202540 7,8,3,9,2,7,7,6,9,2,6,2,0,8,1,2,4,9,2,4,0,1,5,3,6,4,5,4,7,1,6,8,0,8,
%U A202540 6,6,4,3,9,3,8,4,3,2,8,5,4,8,7,9,2,7,9,9,8,0,3,6,1,6,3,6,4,6,4
%N A202540 Decimal expansion of the number x satisfying e^(3x)-e^(-x)=1.
%C A202540 See A202537 for a guide to related sequences. The Mathematica program includes a graph.
%H A202540 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%e A202540 0.19946057824300535148857771838494917839277692...
%t A202540 u = 3; v = 1;
%t A202540 f[x_] := E^(u*x) - E^(-v*x); g[x_] := 1
%t A202540 Plot[{f[x], g[x]}, {x, -2, 2}, {AxesOrigin -> {0, 0}}]
%t A202540 r = x /. FindRoot[f[x] == g[x], {x, .1, .2}, WorkingPrecision -> 110]
%t A202540 RealDigits[r] (* A202540 *)
%t A202540 RealDigits[ Log[ Root[#^4 - # - 1&, 2]], 10, 99] // First (* _Jean-François Alcover_, Feb 27 2013 *)
%o A202540 (PARI) log(polrootsreal(x^4-x-1)[2]) \\ _Charles R Greathouse IV_, May 14 2019
%Y A202540 Cf. A202537.
%K A202540 nonn,cons
%O A202540 0,2
%A A202540 _Clark Kimberling_, Dec 21 2011