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 A078889 #12 Nov 12 2020 05:17:35
%S A078889 1,4,0,8,6,9,2,0,0,2,2,9,6,4,8,3,2,8,1,0,4,3,0,3,8,0,0,5,1,3,5,5,1,1,
%T A078889 3,0,1,0,4,8,7,4,0,7,9,5,1,1,5,8,7,6,5,7,0,4,4,6,8,3,8,8,8,8,6,5,8,8,
%U A078889 4,5,4,8,1,8,9,4,4,7,2,5,6,1,1,6,1,0,1,2,3,4,0,7,1,1,8,4,1,1,0,4,5,5,5,1,9
%N A078889 Decimal expansion of Sum {n>=0} 1/8^(2^n).
%H A078889 Aubrey J. Kempner, <a href="https://doi.org/10.1090/S0002-9947-1916-1501054-4">On Transcendental Numbers</a>, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
%H A078889 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A078889 Equals -Sum_{k>=1} mu(2*k)/(8^k - 1), where mu is the Möbius function (A008683). - _Amiram Eldar_, Jul 12 2020
%e A078889 0.140869200229648328104...
%t A078889 RealDigits[ N[ Sum[1/8^(2^n), {n, 0, Infinity}], 110]][[1]]
%o A078889 (PARI) suminf(n=0, 1/8^(2^n)) \\ _Michel Marcus_, Nov 11 2020
%Y A078889 Cf. A165426.
%Y A078889 Similar sums: A007404, A078885, A078585, A078886, A078887, A078888, A078890, A036987.
%K A078889 cons,nonn
%O A078889 0,2
%A A078889 _Robert G. Wilson v_, Dec 11 2002