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 A211979 #20 Apr 06 2020 19:01:42
%S A211979 110,11100,111110000,1111111000000,111111111110000000000,
%T A211979 1111111111111000000000000,111111111111111110000000000000000,
%U A211979 1111111111111111111000000000000000000,111111111111111111111110000000000000000000000
%N A211979 Numbers n formed by p 1's followed by p - 1 0's, where p is prime(n).
%e A211979 For n = 3, the third prime is 5, so a(3) = 111110000 (five 1's followed by four 0's).
%t A211979 (* Technically this is in base 10 *) Table[10^(Prime[n] - 1)((10^Prime[n] - 1)/9), {n, 20}] (* _Alonso del Arte_, Dec 12 2012 *)
%t A211979 FromDigits[Join[PadRight[{},#,1],PadRight[{},#-1,0]]]&/@ Prime[ Range[ 10]] (* _Harvey P. Dale_, Aug 30 2015 *)
%Y A211979 Binary representation of A060286.
%Y A211979 a(n) has A076274(n) digits.
%Y A211979 Cf. A007088, A076274, A109241, A135650.
%K A211979 nonn,base
%O A211979 1,1
%A A211979 _Omar E. Pol_, Dec 12 2012