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 A139120 #23 Apr 04 2019 03:01:27
%S A139120 10010101,1001010111010111,
%T A139120 100101011101011101011101111101011111011101011101111101111101011111011101011111011101111101111111011101011101011101111111111111011101111101011111111101011111011111011101111101111,
%U A139120 100101011101011101011101111101011111011101011101111101111101011111011101011111011101111101111111011101011101011101111111111111011101111101011111111101011111011111011101111101111101011111111101011101011111111
%N A139120 Primes that show the distribution of prime numbers using "0" for primes and "1" for nonprime numbers.
%C A139120 Primes in A118256.
%C A139120 For n = 1..7, the number of digits in a(n) is 8, 16, 177, 207, 872, 1395, 2114 (no more through 10000). - _Jon E. Schoenfield_, Apr 13 2018
%H A139120 Alois P. Heinz, <a href="/A139120/b139120.txt">Table of n, a(n) for n = 1..5</a>
%H A139120 Caldwell and Honaker, <a href="https://primes.utm.edu/curios/page.php?curio_id=12254">Prime Curios!: 10010101</a>
%t A139120 A118255[n_] := Module[{},
%t A139120 If[n == 1, A118255[1] = 1,
%t A139120 If[PrimeQ[n], A118255[n] = 2 A118255[n - 1],
%t A139120 A118255[n] = 2 A118255[n - 1] + 1]]];
%t A139120 Select[Table[FromDigits[IntegerDigits[A118255[n], 2]], {n, 1, 1000}], PrimeQ] (* _Robert Price_, Apr 03 2019 *)
%Y A139120 Cf. A118255, A118256, A118257, A139101, A139102, A139103, A139104, A139119, A139122.
%K A139120 nonn,base
%O A139120 1,1
%A A139120 _Omar E. Pol_, Apr 11 2008
%E A139120 Extended by _Charles R Greathouse IV_, Jul 27 2009