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 A258086 #13 Jun 12 2021 02:47:49
%S A258086 1,3,5,9,0,9,8,2,7,7,1,1,3,5,4,8,2,6,4,6,4,3,5,2,4,2,0,6,0,7,5,7,2,0,
%T A258086 7,8,7,1,1,2,8,2,8,4,5,1,0,5,1,5,6,8,6,9,4,0,6,0,6,5,2,6,3,1,6,6,5,0,
%U A258086 1,6,5,6,7,1,3,6,5,3,4,2,1,3,0,3,2,9,0,7,6,2,6,4,7,0,9,8,5,5,3,8,3,1,2
%N A258086 Decimal expansion of Integral_{0..infinity} exp(-x)/(1-x*exp(-x)) dx.
%H A258086 MathOverflow, <a href="http://mathoverflow.net/questions/206917">Upper bound of the waiting time of a sum process.</a>
%F A258086 c = Sum_{i >= 0} i!/(i+1)^(i+1).
%F A258086 Equals Integral_{-exp(-1)..0} (LambertW(x)-LambertW(-1,x))/(1+x)^2 dx. - _Gleb Koloskov_, Jun 12 2021
%e A258086 1.35909827711354826464352420607572078711282845105156869406...
%p A258086 evalf(Int(exp(-x)/(1-x*exp(-x)),x=0..infinity),120); # _Vaclav Kotesovec_, May 19 2015
%t A258086 c = NIntegrate[Exp[-x]/(1-x*Exp[-x]), {x, 0, Infinity}, WorkingPrecision -> 103]; RealDigits[c] // First
%o A258086 (PARI) default(realprecision,120); sumpos(k=0, k!/(k+1)^(k+1)) \\ _Vaclav Kotesovec_, May 19 2015
%K A258086 nonn,cons,easy
%O A258086 1,2
%A A258086 _Jean-François Alcover_, May 19 2015