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 A089215 #28 Jun 25 2022 22:53:56
%S A089215 1,2,3,2,4,3,2,3,5,4,3,4,2,3,4,3,6,5,4,5,3,4,5,4,2,3,4,3,5,4,3,4,7,6,
%T A089215 5,6,4,5,6,5,3,4,5,4,6,5,4,5,2,3,4,3,5,4,3,4,6,5,4,5,3,4,5,4,8,7,6,7,
%U A089215 5,6,7,6,4,5,6,5,7,6,5,6,3,4,5,4,6,5,4,5,7,6,5,6,4,5,6,5,2,3,4,3,5,4,3,4,6
%N A089215 Thue-Morse sequence on the integers.
%C A089215 Sequence is S(infinity) where S(1)={1,2} and S(n+1)=S(n)S'(n) where S'(n) is obtained from S(n) by substituting an element x of S(n) with M(n)-x where M(n)=2+Max{S(n)}.
%C A089215 For comparison, the Thue-Morse sequence on alphabet {1,2} is constructed as follows: S(1)={1,2} and S(n+1)=S(n)S'(n) where S'(n) is obtained from S(n) by substituting an element x of S(n) with 3-x.
%F A089215 Sum_{k=1..n} a(k) is asymptotic to C*n*log(n) with C=0.8....
%F A089215 a(n) = A209281(n) + 1. - _Kevin Ryde_, Jun 25 2022
%e A089215 S(1)={1,2} then M(1)=4 and S'(1)={4-1,4-2}={3,2}. So S(2)={1,2,3,2}. M(2)=5 so S(3)={1,2,3,2}{5-1,5-2,5-3,5-2} and sequence begins 1,2,3,2,4,3,2,3,...
%o A089215 (PARI) a(n) = n--; my(s=1,h); while((h = n>>s), n=bitxor(n,h); s<<=1); hammingweight(n) + 1; \\ _Kevin Ryde_, Jun 25 2022
%Y A089215 Cf. A001285, A209281.
%K A089215 nonn,easy
%O A089215 1,2
%A A089215 _Benoit Cloitre_, Dec 10 2003