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 A280737 #12 Feb 25 2023 06:46:24 %S A280737 0,0,1,0,1,1,1,0,1,1,2,1,2,1,1,0,1,1,2,1,2,2,2,1,2,2,2,1,2,1,1,0,1,1, %T A280737 2,1,2,2,2,1,2,2,3,2,3,2,2,1,2,2,3,2,3,2,2,1,2,2,2,1,2,1,1,0,1,1,2,1, %U A280737 2,2,2,1,2,2,3,2,3,2,2,1,2,2,3,2,3,3,3,2,3,3,3,2,3,2,2,1,2,2,3 %N A280737 a(n) = A007302(n) - 1. %H A280737 Vincenzo Librandi, <a href="/A280737/b280737.txt">Table of n, a(n) for n = 1..10000</a> %H A280737 Alma D'Aniello, Aldo de Luca, and Alessandro De Luca, <a href="http://arxiv.org/abs/1602.03231">On Christoffel and standard words and their derivatives</a>, arXiv:1602.03231 [cs.DM], 2016 (mentions this sequence). %o A280737 (PARI) a(n)=hammingweight(bitxor(n,3*n))-1; \\ _Joerg Arndt_, Feb 25 2023 %Y A280737 Cf. A007302. %K A280737 nonn %O A280737 1,11 %A A280737 _N. J. A. Sloane_, Jan 11 2017