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 A138722 #4 Feb 05 2017 11:59:51
%S A138722 110011,111000111,111110000011111,111111100000001111111,
%T A138722 111111111110000000000011111111111,
%U A138722 111111111111100000000000001111111111111
%N A138722 Concatenation of p digits 1, p digits 0 and p digits 1, where p is the n-th prime.
%t A138722 Table[FromDigits[Join[PadRight[{},n,1],PadRight[{},n,0],PadRight[{},n,1]]],{n,Prime[Range[7]]}] (* _Harvey P. Dale_, Feb 05 2017 *)
%Y A138722 Cf. A000040, A138149, A138721.
%K A138722 base,easy,nonn
%O A138722 1,1
%A A138722 _Omar E. Pol_, Mar 29 2008