cp's OEIS Frontend

A275306 Decimal expansion of 1/2 - Sum_{k>=1} 1/2^prime(k).

%I A275306 #38 Feb 16 2025 08:33:36
%S A275306 0,8,5,3,1,7,4,9,0,1,4,8,8,8,8,3,3,9,7,5,1,8,9,0,3,7,7,8,4,5,6,9,2,2,
%T A275306 9,1,6,3,4,2,2,5,7,6,1,8,6,2,0,8,3,0,2,2,1,3,1,7,5,4,5,8,5,5,1,1,3,5,
%U A275306 9,0,3,9,3,8,0,6,4,2,6,6,5,8,0,3,7,0,9,9,5,1,5,7,1,5,2,4,2,2,2,0,6,0,3,8,3,8,4,0,6,4,7,9,1,7,0,1,4,0,4,2,1
%N A275306 Decimal expansion of 1/2 - Sum_{k>=1} 1/2^prime(k).
%C A275306 Composite constant: decimal value of A066247 interpreted as a binary number.
%C A275306 The characteristic function of composite numbers (A066247) has values 0, 0, 0, 1, 0, 1, 0, 1, 1, ... for n = 1, 2, 3, ... The constant obtained by concatenating these digits and interpreting them as a binary fraction is therefore C = 0.0001010111010... (base 2) = 0.0853174901...(base 10).
%C A275306 Continued fraction [0; 11, 1, 2, 1, 1, 2, 1, 1, 131, 2, 1, 1, 2, 6, 4, 2, 21, ...].
%H A275306 Simon Plouffe, <a href="http://www.plouffe.fr/simon/constants/primesbin.txt">Primes coded in binary to 1000 digits</a>.
%H A275306 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CompositeNumber.html">Composite Number</a>.
%H A275306 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeConstant.html">Prime Constant</a>.
%F A275306 Equals Sum_{k>=1} 1/2^A002808(k).
%F A275306 From _Amiram Eldar_, Aug 11 2020: (Start)
%F A275306 Equals Sum_{k>=1} 1/A073718(k).
%F A275306 Equals Sum_{k>=1} A066247(k)/2^k.
%F A275306 Equals -(1/2) + Sum_{k>=1} A062298(k)/2^(k+1). (End)
%F A275306 Equals Sum_{k >= 1} ((-1)^A010051(k))/2^(k+1). - _Antonio Graciá Llorente_, Jan 13 2024
%e A275306 0.0853174901... = (0.00010101110...)_2.
%e A275306                         | | |||
%e A275306                         4 6 8910
%t A275306 nn = 121; Take[#, nn] &@ PadLeft[First@ #, Abs@ Last@ # + Length@ First@ #] &@ RealDigits@ N[1/2 - Sum[ 1/2^Prime[k], {k, 10^4}], nn + 2] (* _Michael De Vlieger_, Jul 22 2016 *)
%o A275306 (PARI) s=.5; forprime(p=2,bitprecision(s)+2, s-=1.>>p); s \\ _Charles R Greathouse IV_, Jul 22 2016
%Y A275306 Cf. A002808, A051006, A005171, A062298, A066247, A073718.
%K A275306 nonn,cons
%O A275306 0,2
%A A275306 _Ilya Gutkovskiy_, Jul 22 2016