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 A356023 #33 Dec 10 2023 09:27:28
%S A356023 7,5,0,2,4,4,1,4,0,6,2,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T A356023 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A356023 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N A356023 Decimal expansion of Sum_{j>=1} 2^^j/2^^(j+1) where ^^ indicates tetration.
%C A356023 This series converges quickly and a very good approximation of this constant is given by the first three terms, 2/2^2 + 2^2/2^2^2 + 2^2^2/2^2^2^2 = 3073/4096, since the next term 2^2^2^2/2^2^2^2^2 is about 1/10^19723.4853.
%e A356023 0.750244140625...
%t A356023 RealDigits[Total[Most[(s = NestList[2^# &, 2, 4])]/Rest[s]], 10, 100][[1]] (* _Amiram Eldar_, Jul 23 2022 *)
%Y A356023 Cf. A356022.
%K A356023 nonn,cons
%O A356023 0,1
%A A356023 _Marco Ripà_, Jul 23 2022