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 A286577 #9 May 31 2017 16:15:54 %S A286577 0,1,1,3,4,1,6,7,3,9,10,4,12,13,1,15,16,6,18,19,7,21,22,3,24,25,9,27, %T A286577 28,10,30,31,4,33,34,12,36,37,13,39,40,1,42,43,15,45,46,16,48,49,6,51, %U A286577 52,18,54,55,19,57,58,7,60,61,21,63,64,22,66,67,3,69,70,24,72,73,25,75,76,9,78,79,27,81,82,28,84,85,10,87,88,30,90 %N A286577 If n = 3k-1 then a(n) = a(k), otherwise a(n) = n. %H A286577 Antti Karttunen, <a href="/A286577/b286577.txt">Table of n, a(n) for n = 0..10001</a> %F A286577 If n = 3k-1 then a(n) = a(k), otherwise a(n) = n. %o A286577 (Scheme) (define (A286577 n) (if (= 2 (modulo n 3)) (A286577 (/ (+ 1 n) 3)) n)) %Y A286577 Cf. A000265, A007051 (gives the positions of ones), A286578. %K A286577 nonn %O A286577 0,4 %A A286577 _Antti Karttunen_, May 31 2017