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 A098725 #11 Apr 04 2024 10:04:39 %S A098725 0,1,1,1,0,1,1,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,0,1,0,1, %T A098725 1,1,0,1,1,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1,0,1,0,1,1,1, %U A098725 0,1,1,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1 %N A098725 a(4n) = 0, a(2n+1) = 1, a(4n+2) = a(n+1). %C A098725 Apparently, the first differences of A072894. %H A098725 Antti Karttunen, <a href="/A098725/b098725.txt">Table of n, a(n) for n = 0..65537</a> %H A098725 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a> %t A098725 A098725[n_] := Which[OddQ[n], 1, Divisible[n, 4], 0, True, A098725[(n+2)/4]]; %t A098725 Array[A098725, 100, 0] (* _Paolo Xausa_, Apr 04 2024 *) %o A098725 (PARI) a(n)=if(n%2==1,1,if(n%4==0,0,a((n-2)/4+1))) %K A098725 nonn %O A098725 0,1 %A A098725 _Ralf Stephan_, Oct 15 2004