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 A175186 #13 Oct 30 2019 15:18:22
%S A175186 0,1,1,3,1,3,4,7,1,3,4,7,6,9,11,15,1,3,4,7,6,9,11,15,10,13,15,19,19,
%T A175186 23,26,31,1,3,4,7,6,9,11,15,10,13,15,19,19,23,26,31,18,21,23,27,27,31,
%U A175186 34,39,35,39,42,47,48,53,57,63,1,3,4,7,6,9,11,15,10,13,15,19,19,23,26,31
%N A175186 a(1)=0. For 1<= n <= 2^m, m>=0, a(n+ 2^m) = a(n)+n.
%C A175186 a(2^m) = 2^m -1.
%t A175186 f[l_]:=Join[l,l+Range[Length[l]]]; Nest[f,{0},7] (* _Ray Chandler_, Mar 04 2010 *)
%Y A175186 Cf. A083741, A175187.
%K A175186 easy,nonn
%O A175186 1,4
%A A175186 _Leroy Quet_, Mar 01 2010
%E A175186 Extended by _Ray Chandler_, Mar 04 2010