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 A001391 #13 Apr 04 2017 04:46:20 %S A001391 10,1110,11110,100110,1110010110,111100111010110, %T A001391 100110011110111010110,1110010110010011011110111010110, %U A001391 1111001110101100111001011010011011110111010110 %N A001391 To get the 3rd term, for example, note that 2nd term has three (11 in binary!) 1's and one (1) 0, giving 11 1 1 0. %H A001391 John Cerkan, <a href="/A001391/b001391.txt">Table of n, a(n) for n = 1..17</a> %Y A001391 Cf. A001387. %K A001391 nonn,base %O A001391 1,1 %A A001391 _N. J. A. Sloane_, _Thomas L. York_