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 A238270 #18 Jul 07 2023 13:20:19
%S A238270 1,0,2,0,1,1,3,3,4,8,1,7,8,1,0,3,6,4,7,4,3,0,3,6,3,9,3,9,3,1,8,2,4,3,
%T A238270 5,1,5,4,3,6,1,0,4,9,2,5,1,0,2,9,1,0,7,3,5,8,7,3,8,8,0,3,2,5,9,0,9,3,
%U A238270 7,2,7,6,0,5,1,9,5,2,3,3,8,4,2,8,4,8,3,6,8,4,7,8,5,5,2,0,3,8,8,9,6,6,7,3,7,2
%N A238270 Decimal expansion of Sum_{n>=1} mu(n)/2^n.
%C A238270 Suggested by a posting to SeqFan list by _Alonso del Arte_ at 15:35 on Aug 09 2012.
%e A238270 0.102011334817810364743036393931824351543610492510291073587388032...
%t A238270 RealDigits[ Sum[ N[ MoebiusMu[n] 2^-n, 128], {n, 380}], 10, 111][[1]]
%o A238270 (PARI) sum(n=1,(default(realprecision)+2)*log(10)/log(2),moebius(n)/2.^n) \\ _Charles R Greathouse IV_, Sep 03 2015
%Y A238270 Cf. A008683, A238271, A181673, A238273.
%K A238270 nonn,cons,easy
%O A238270 0,3
%A A238270 _Robert G. Wilson v_, Feb 21 2014