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 A264936 #17 Sep 07 2018 17:34:00
%S A264936 4,5,5,5,5,7,0,3,6,7,0,1,9,5,8,4,2,9,0,0,4,9,5,0,0,0,4,7,0,4,0,7,0,5,
%T A264936 7,7,0,4,9,0,3,9,3,3,9,6,9,1,2,1,7,1,7,0,6,0,7,3,0,2,3,6,0,9,6,7,6,4,
%U A264936 2,5,3,0,9,7,2,2,4,7,6,2,2,4,4,8,9,0,0,2,5,0,1,4,0,1,0,5,0,7,7,6,8,5,3,7,8,6
%N A264936 Decimal expansion of the positive root of x^(x^x) = gamma.
%H A264936 G. C. Greubel, <a href="/A264936/b264936.txt">Table of n, a(n) for n = 0..10000</a>
%H A264936 Wikipedia, <a href="https://en.wikipedia.org/wiki/Euler%E2%80%93Mascheroni_constant">Euler-Mascheroni constant</a>
%e A264936 0.4555570367019584290049500047040705770490...
%t A264936 Take[RealDigits[x /. FindRoot[x^x^x == EulerGamma, {x, 1}, WorkingPrecision -> 120]][[1]], 100] (* _G. C. Greubel_, Sep 07 2018 *)
%o A264936 (PARI) default(realprecision,2000); solve(x=0.4,0.5,x^(x^x)-Euler)
%Y A264936 Cf. A001620.
%K A264936 nonn,cons
%O A264936 0,1
%A A264936 _Anders Hellström_, Nov 28 2015
%E A264936 More digits from _Jon E. Schoenfield_, Mar 15 2018