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 A130819 #19 Oct 01 2022 06:08:45
%S A130819 2,4,4,4,6,6,6,6,6,8,8,8,8,8,8,8,10,10,10,10,10,10,10,10,10,12,12,12,
%T A130819 12,12,12,12,12,12,12,12,14,14,14,14,14,14,14,14,14,14,14,14,14,16,16,
%U A130819 16,16,16,16,16,16,16,16,16,16,16,16,16,18,18,18,18,18,18,18,18,18,18,18
%N A130819 2*k appears 2*k-1 times.
%C A130819 The run-length encoding of this sequence is A000027 as it has one 2, three 4's, five 6's, and so on. - _Alexander Fraebel_, Sep 10 2012
%F A130819 Sum_{n>=1} (-1)^(n+1)/a(n) = log(2)/2. - _Amiram Eldar_, Oct 01 2022
%Y A130819 Equals twice A003059. - _Michel Marcus_, Sep 14 2020
%Y A130819 Cf. A000027.
%K A130819 nonn
%O A130819 1,1
%A A130819 _Paul Curtz_, Jul 17 2007