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 A139103 #21 Apr 04 2019 03:01:05
%S A139103 10,100,10010,1001010,10010101110,1001010111010,10010101110101110,
%T A139103 1001010111010111010,10010101110101110101110,
%U A139103 10010101110101110101110111110,1001010111010111010111011111010,1001010111010111010111011111010111110,10010101110101110101110111110101111101110
%N A139103 Numbers that show the distribution of prime numbers up to the n-th prime using "0" for primes and "1" for nonprime numbers.
%C A139103 a(n) has A000040(n) digits, n digits "0" and A000040(n)-n digits "1".
%H A139103 Omar E. Pol, <a href="http://polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>.
%t A139103 Table[ sum = 0; For[i = 1, i <= Prime[n] , i++, sum = sum*2;
%t A139103 If[! PrimeQ[i], sum++]]; IntegerString[sum, 2], {n, 1, 20}] (* _Robert Price_, Apr 03 2019 *)
%o A139103 (PARI) a(n) = fromdigits(vector(prime(n), k, !isprime(k)), 10); \\ _Michel Marcus_, Apr 04 2019
%Y A139103 Binary representation of A139104.
%Y A139103 Subset of A118256.
%Y A139103 Cf. A139101, A139102, A139119, A139120, A139122.
%K A139103 nonn,base
%O A139103 1,1
%A A139103 _Omar E. Pol_, Apr 08 2008
%E A139103 a(12)-a(13) from _Robert Price_, Apr 03 2019