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 A333229 #4 Mar 18 2020 23:02:30 %S A333229 3,4,3,2,3,3,3,4,3,3,4,3,2,3,3,2,3,4,3,3,3,2,3,3,3,4,3,2,3,3,2,3,3,3, %T A333229 4,3,3,4,3,2,3,3,3,4,3,3,3,2,3,3,2,3,4,3,3,4,3,2,3,3,3,4,3,3,4,3,2,3, %U A333229 3,2,3,3,3,4,3,3,3,2,3,4,3,3,4,3,2,3,3 %N A333229 First sums of the Kolakoski sequence A000002. %F A333229 a(n) = A000002(n) + A000002(n + 1). %t A333229 kolagrow[q_]:=If[Length[q]<2,Take[{1,2},Length[q]+1],Append[q,Switch[{q[[Length[Split[q]]]],q[[-2]],Last[q]},{1,1,1},0,{1,1,2},1,{1,2,1},2,{1,2,2},0,{2,1,1},2,{2,1,2},2,{2,2,1},1,{2,2,2},1]]] %t A333229 kol[n_Integer]:=Nest[kolagrow,{1},n-1]; %t A333229 Table[kol[n][[-1]]+kol[n+1][[-1]],{n,30}] %Y A333229 Positions of 3's are A054353. %Y A333229 Positions of 2's are A074262. %Y A333229 Positions of 4's are A074263. %Y A333229 The number of runs in the first n terms of A000002 is A156253(n). %Y A333229 Even-indexed terms are A332273 (without the first term). %Y A333229 Odd-indexed terms are A332875. %Y A333229 Cf. A000002, A001462, A013947, A013948, A088568, A156728, A288605, A296658, A329315, A329316, A329317, A329362. %K A333229 nonn %O A333229 1,1 %A A333229 _Gus Wiseman_, Mar 18 2020