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 A138885 #5 May 26 2023 17:44:13
%S A138885 1,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
%T A138885 0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,
%U A138885 1,1,1,1,1,1,1,1,1,1,1
%N A138885 n-th run has length n-th nonprime number, with digits 0 and 1 only, starting with 1.
%e A138885 .n ..... Run ................... Length
%e A138885 .1 ..... 1 ..................... 1
%e A138885 .2 ..... 0,0,0,0 ............... 4
%e A138885 .3 ..... 1,1,1,1,1,1 ........... 6
%e A138885 .4 ..... 0,0,0,0,0,0,0,0 ....... 8
%e A138885 .5 ..... 1,1,1,1,1,1,1,1,1 ..... 9
%t A138885 Join[{1},{PadRight[{},#[[1]],0],PadRight[{},#[[2]],1]}&/@Partition[Select[Range[ 20],CompositeQ],2]]//Flatten (* _Harvey P. Dale_, May 26 2023 *)
%Y A138885 Nonprime numbers: A018252. Cf. A057211, A138149, A138150, A138709, A138710, A138711, A138712, A138886.
%K A138885 easy,nonn
%O A138885 1,1
%A A138885 _Omar E. Pol_, Apr 06 2008