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 A026498 #18 Oct 07 2019 14:45:44 %S A026498 2,2,2,1,2,2,2,2,2,2,2,1,2,1,1,1,2,2,2,1,2,2,2,2,2,2,2,2,1,2,2,2,2,2, %T A026498 2,1,2,2,2,2,2,2,2,1,2,1,1,1,2,2,2,1,2,1,1,1,1,1,1,1,2,1,1,1,2,2,2,1, %U A026498 2,2,2,2,2,2,2,1,2,1,1,1,2,2,2,1,2,2,2,2,2,2 %N A026498 a(n) = t(1+3n), where t = A001285 (Thue-Morse sequence). %H A026498 Michael De Vlieger, <a href="/A026498/b026498.txt">Table of n, a(n) for n = 0..10000</a> %t A026498 Array[1 + Mod[DigitCount[3 # + 1, 2, 1], 2] &, 105, 0] (* _Michael De Vlieger_, Oct 03 2019 *) %o A026498 (PARI) a(n)=1+hammingweight(3*n+1)%2 \\ _Charles R Greathouse IV_, May 09 2016 %Y A026498 Cf. A001285, A026492, A026513. %K A026498 nonn %O A026498 0,1 %A A026498 _Clark Kimberling_ %E A026498 Name and Pari adapted to match offset in A001285 by _Sean A. Irvine_, Oct 03 2019