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 A104606 #2 Mar 30 2012 17:31:12
%S A104606 1,0,1,0,1,0,1,0,0,1,0,0,1,1,1,1,1,0,1,1,0,1,1,1,0,0,1,1,0,0,0,1,1,1,
%T A104606 1,1,0,1,0,0,0,0,1,1,0,0,0,1,0,0,0,1,0,1,1,1,0,1,1,1,1,0,0,1,1,1,0,1,
%U A104606 1,0,1,1,0,1,1,0,0,1,1,0,0,1,1,0,1,0,1,1,1,1,0,1,0,1,0,1,0,1,0,0,1,1,0,1,0
%N A104606 Write the natural numbers in base 2 in a triangle with k digits in the k-th row, as shown below. Sequence gives the leading diagonal.
%C A104606 1
%C A104606 10
%C A104606 111
%C A104606 0010
%C A104606 11101
%C A104606 111000...
%t A104606 t = Flatten[ IntegerDigits[ Range[660], 2]]; t[[Table[n(n + 1)/2, {n, 105}]]]
%Y A104606 Cf. A104607, A104608, A104609, A104610, A104611, A104612, A104613, A091425, A104614, A104615, A104616, A104617, A104618, A104619, A104620.
%K A104606 base,nonn
%O A104606 1,1
%A A104606 _Robert G. Wilson v_, Mar 16 2005