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 A126583 #23 Feb 16 2025 08:33:04
%S A126583 7,0,3,4,6,7,4,2,2,4,9,8,3,9,1,6,5,2,0,4,9,8,1,8,6,0,1,8,5,9,9,0,2,1,
%T A126583 3,0,3,4,2,9,2,8,4,3,1,0,3,4,2,2,3,6,0,8,0,9,3,2,8,7,6,9,2,2,1,9,9,2,
%U A126583 1,2,2,1,4,4,0,6,7,7,4,2,1,7,9,3,6,6,4,6,0,7,6,6,4,3,8,3,1,3,8,5,4,7
%N A126583 Decimal expansion of solution to exp(-x) = x^2.
%C A126583 The value of the infinite power tower function x^x^x... at x = sqrt(1/e). - _Alois P. Heinz_, Oct 19 2016
%H A126583 G. C. Greubel, <a href="/A126583/b126583.txt">Table of n, a(n) for n = 0..10000</a>
%H A126583 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PowerTower.html">Power Tower</a>
%H A126583 Wikipedia, <a href="http://en.wikipedia.org/wiki/Tetration">Tetration</a>
%H A126583 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A126583 Equals 2*LambertW(1/2). - _Alois P. Heinz_, Oct 19 2016
%F A126583 Equals log(A099554) = 2*A202356. - _Hugo Pfoertner_, Jul 19 2024
%e A126583 0.7034674224983916520498186018599021303429284310342236...
%t A126583 RealDigits[ FindRoot[ Exp[ -x] == x^2, {x, {.5, 1}}, WorkingPrecision -> 120][[1, 2, 1]], 10, 111][[1]]
%t A126583 RealDigits[ 2*ProductLog[1/2], 10, 102] // First (* _Jean-François Alcover_, Feb 27 2013 *)
%o A126583 (PARI) 2*lambertw(1/2) \\ _G. C. Greubel_, Mar 06 2018
%Y A126583 Cf. A030178, A099554, A202356.
%K A126583 cons,nonn
%O A126583 0,1
%A A126583 Denton J. Dailey (djd1497(AT)aol.com), Jan 05 2007