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 A371135 #6 Mar 12 2024 02:47:35
%S A371135 7,9,9,0,7,3,2,1,9,8,2,3,2,7,2,3,9,9,4,4,1,0,6,4,3,2,3,2,1,0,0,5,0,6,
%T A371135 4,5,3,1,7,2,2,2,4,6,5,3,9,8,5,2,9,3,3,3,2,9,0,2,0,9,1,2,5,8,6,8,5,9,
%U A371135 4,6,2,8,9,9,4,7,8,6,2,6,1,1,7,8,0,3,9,2,2,4,6,6,8,9,2,2,3,7,4,3,8,5,7,8,7,1,8,5,5,0,5,9,6,1,8,8,6,2,6,2
%N A371135 Decimal expansion of Sum_{powerful k>=1} k / 2^k.
%C A371135 Chen and Ruzsa (1999) proved that this constant is irrational.
%H A371135 Yong-Gao Chen and Imre Z. Ruzsa, <a href="https://doi.org/10.1023/A:1004742930674">On the irrationality of certain series</a>, Periodica Mathematica Hungarica, Vol. 38, No. 1 (1999), pp. 31-37.
%F A371135 Equals Sum_{k>=1} A001694(k) / 2^A001694(k).
%F A371135 Equals Sum_{k>=1} k * A112526(k) / 2^k.
%e A371135 0.79907321982327239944106432321005064531722246539852...
%t A371135 RealDigits[Sum[n/2^n, {n, Select[Range[1000], # == 1 || Min[FactorInteger[#][[;; , 2]]] > 1 &]}], 10, 120][[1]]
%Y A371135 Cf. A001694, A112526, A346173, A371134.
%K A371135 nonn,cons
%O A371135 0,1
%A A371135 _Amiram Eldar_, Mar 12 2024