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 A279210 #20 Oct 12 2018 04:41:26
%S A279210 0,0,0,0,0,1,0,0,0,1,1,2,0,1,0,0,0,1,1,2,1,1,2,3,0,1,1,2,0,1,0,0,0,1,
%T A279210 1,2,1,1,2,3,1,1,1,1,2,2,3,4,0,1,1,2,1,1,2,3,0,1,1,2,0,1,0,0,0,1,1,2,
%U A279210 1,1,2,3,1,1,1,1,2,2,3,4,1,1,1,1,1,1,1,1,2,2,2,2,3,3,4,5,0,1,1,2,1
%N A279210 Length of second run of 1's in binary expansion of n.
%H A279210 Michael De Vlieger, <a href="/A279210/b279210.txt">Table of n, a(n) for n = 0..10000</a>
%F A279210 a(2*n) = a(n). - _David A. Corneth_, Oct 12 2018
%e A279210 46 = 101110_2 so a(46) = 3.
%t A279210 Table[First[Map[Length, Rest@ DeleteCases[#, w_ /; First@ w == 0] &@ Split@ IntegerDigits[n, 2]] /. {} -> {0}], {n, 100}] (* _Michael De Vlieger_, Dec 23 2016 *)
%Y A279210 Cf. A090996, A279209.
%K A279210 nonn,base
%O A279210 0,12
%A A279210 _N. J. A. Sloane_, Dec 22 2016
%E A279210 More terms from _Michael De Vlieger_, Dec 23 2016