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 A272413 #6 Feb 16 2025 08:33:34
%S A272413 2,0,9,5,8,0,8,7,4,2,8,4,1,8,5,8,1,3,9,8,9,0,2,9,6,5,7,8,1,5,3,4,9,5,
%T A272413 5,6,9,0,1,1,3,1,0,3,2,0,1,6,2,3,4,3,3,0,0,0,6,9,2,1,5,9,8,8,1,4,8,5,
%U A272413 3,1,0,8,8,4,6,4,2,8,7,2,6,3,4,2,8,7,1,6,3,6,8,2,9,8,8,3,4,7
%N A272413 Asymptotic mean (normalized by n) of the second longest cycle in a random permutation on n symbols.
%D A272413 Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.4 Golomb-Dickman Constant, p. 285.
%H A272413 Xavier Gourdon, <a href="http://algo.inria.fr/gourdon/thesis.html">Combinatoire, Algorithmique et Géométrie des Polynomes</a> Ecole Polytechnique, Paris 1996, page 152 [in French]
%H A272413 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/Golomb-DickmanConstant.html">Golomb-Dickman Constant</a>
%H A272413 Wikipedia, <a href="http://en.wikipedia.org/wiki/Golomb%E2%80%93Dickman_constant">Golomb-Dickman constant</a>
%F A272413 Integral_{0..infinity} 1 - exp(Ei(-x))*(1 - Ei(-x)) dx, where Ei is the exponential integral.
%e A272413 0.20958087428418581398902965781534955690113103201623433...
%t A272413 digits = 98; NIntegrate[1 - Exp[ExpIntegralEi[-x]]*(1 - ExpIntegralEi[-x]), {x, 0, 200}, WorkingPrecision -> digits+5] // RealDigits[#, 10, digits]& // First
%Y A272413 Cf. A084945, A247398.
%K A272413 nonn,cons
%O A272413 0,1
%A A272413 _Jean-François Alcover_, Apr 29 2016