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 A237421 #14 Nov 30 2014 14:25:19
%S A237421 6,0,3,2,3,2,6,8,3,7,7,4,1,3,6,2,0,6,2,2,0,1,9,2,6,5,0,9,4,8,6,6,8,2,
%T A237421 2,0,4,2,0,9,6,2,5,1,4,2,1,1,7,4,8,7,4,8,0,4,2,4,0,3,6,1,5,4,8,8,9,6,
%U A237421 6,5,7,3,0,6,0,4,3,0,0,6,9,7,3,8,3,0,3,2,1,9,2,7,2,3,5,2,6,2,5,4,7,6,9,7,7,3
%N A237421 Decimal expansion of the root of the equation (1-r)^(2*r) = r^(2*r+1).
%H A237421 Vaclav Kotesovec, <a href="/A237421/b237421.txt">Table of n, a(n) for n = 0..105</a>
%e A237421 0.6032326837741362...
%p A237421 Digits:= 140:
%p A237421 v:= convert(fsolve((1-r)^(2*r) = r^(2*r+1), r=1/2), string):
%p A237421 seq(parse(v[n+2]), n=0..120);
%t A237421 RealDigits[r/.FindRoot[(1-r)^(2*r)==r^(2*r+1), {r, 1/2}, WorkingPrecision->250], 10, 200][[1]]
%Y A237421 Cf. A206152, A227403, A220359.
%K A237421 nonn,cons
%O A237421 0,1
%A A237421 _Vaclav Kotesovec_, Mar 04 2014