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 A135540 #9 Oct 19 2016 03:04:43
%S A135540 1,3,1,7,3,3,1,15,7,7,3,7,3,3,1,31,15,15,7,15,7,7,3,15,7,7,3,7,3,3,1,
%T A135540 63,31,31,15,31,15,15,7,31,15,15,7,15,7,7,3,31,15,15,7,15,7,7,3,15,7,
%U A135540 7,3,7,3,3,1,127,63,63,31,63,31,31,15,63,31,31,15,31,15,15,7,63,31,31,15,31,15
%N A135540 a(n) = 2^(A000523(n) - A000120(n) + 2) - 1.
%H A135540 G. C. Greubel, <a href="/A135540/b135540.txt">Table of n, a(n) for n = 1..1000</a>
%F A135540 a(n) = 2^(floor(log_2(n)) - (n - Sum_{k=1,..,n}[floor(n/2^k)]) + 2) - 1. - _G. C. Greubel_, Oct 18 2016
%p A135540 GS(6,3,200); [see A135416].
%t A135540 Table[2^(Floor[Log[2, n]] - (n - Sum[Floor[n/2^k], {k, 1, n}]) + 2) - 1, {n,1,25}] (* _G. C. Greubel_, Oct 18 2016 *)
%Y A135540 Cf. A135416.
%Y A135540 This is Guy Steele's sequence GS(6, 3) (see A135416).
%K A135540 nonn
%O A135540 1,2
%A A135540 _N. J. A. Sloane_, based on a message from Guy Steele and _Don Knuth_, Mar 01 2008