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 A111123 #42 Jul 14 2021 21:22:27
%S A111123 1,2,2,3,5,8,11,16,25,38,57,85,127,192,289,430,644,966,1450,2173,3263,
%T A111123 4899,7341,11022,16526,24802,37201,55808,83702,125541,188301,282444,
%U A111123 423683,635569,953356,1429969,2144990,3217454,4826176,7239129,10858479,16287972,24431890
%N A111123 Number of 2's in n-th "Kolakoski" string defined in A054349.
%C A111123 Also the number of terms in n-th string (starting from n=3) when representing A000002 as a tree. Each branch of this tree is a string. Starting from n=3, each 1 in n-th string generates either 1 or 2 in (n+1)-th string and each 2 in n-th string generates either 11 or 22 in (n+1)-th string based on the previously generated term of either 2 or 1. Hence, the number of terms in (n+1)-th string is the sum of all terms in n-th string. - _Rakesh Khanna A_, May 24 2020
%H A111123 Rakesh Khanna A, <a href="/A111123/b111123.txt">Table of n, a(n) for n = 0..59</a>
%F A111123 a(0) + a(1) + ... + a(n) = A042942(n+2) - 1.
%F A111123 a(n) = A001083(n+4) - A001083(n+3). - _Benoit Cloitre_, Nov 07 2010
%t A111123 l = { (*terms in A042942*) }; For[i = 2, i <= Length[l], i++, Print[l[[i]] - l[[i - 1]]]]
%Y A111123 Cf. A001083, A042942, A054349, A111124 (number of 1's).
%K A111123 nonn
%O A111123 0,2
%A A111123 _Benoit Cloitre_, Oct 16 2005
%E A111123 More terms from and offset changed to 0 by _Jinyuan Wang_, Apr 03 2020