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 A247146 #43 Jul 15 2022 13:49:07
%S A247146 0,1,1,3,1,7,1,11,5,19,1,47,1,67,21,139,1,295,1,539,69,1027,1,2223,17,
%T A247146 4099,261,8267,1,16951,1,32907,1029,65539,81,133423,1,262147,4101,
%U A247146 524955,1,1056871,1,2098187,16661,4194307,1,8423599,65,16777747,65541
%N A247146 As a binary numeral, the bit 2^(m-1) of a(n) is 1 iff m is a proper divisor of n.
%C A247146 a(n)==1 iff n is prime.
%C A247146 Apparently Moebius transform of A178472.
%C A247146 For n>1, the binary representation of a(n) is given by row (n-1) of A077049 (when read as a triangular array). - _Tom Edgar_, Nov 28 2014
%F A247146 a(n) = A034729(n) - 2^(n-1). - _Michel Marcus_, Nov 22 2014
%t A247146 With[{n=Range[100]},(1/2) ((Total/@(2^Divisors[n])) - 2^n)]
%o A247146 (PARI) a(n) = sumdiv(n, k, 2^(k-1)) - 2^(n-1); \\ _Michel Marcus_, Nov 25 2014
%o A247146 (Python)
%o A247146 from sympy import divisors
%o A247146 def A247146(n): return sum(1<<d-1 for d in divisors(n,generator=True) if d<n) # _Chai Wah Wu_, Jul 15 2022
%Y A247146 Cf. A034729, A077049, A178472.
%K A247146 nonn
%O A247146 1,4
%A A247146 _Morgan L. Owens_, Nov 21 2014