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 A189674 #16 Apr 24 2021 03:30:08 %S A189674 0,1,1,2,3,3,3,4,4,5,6,6,7,8,8,8,9,9,9,10,10,11,12,12,12,13,13,14,15, %T A189674 15,16,17,17,17,18,18,19,20,20,21,22,22,22,23,23,23,24,24,25,26,26,26, %U A189674 27,27,27,28,28,29,30,30,30,31,31,32,33,33,34,35,35,35,36,36,36,37,37,38,39,39,39,40,40 %N A189674 Partial sums of A189673. %C A189674 See A189673. %H A189674 Kevin Ryde, <a href="http://user42.tuxfamily.org/terdragon/index.html">Iterations of the Terdragon Curve</a>, see index "TurnsL", with a(n) = TurnsL(n-1). %F A189674 a(n) = a(floor((n+2)/3)) + floor((n+1)/3), where a(1)=0. %t A189674 (See A189673.) %o A189674 (PARI) a(n) = n--; (n + vecsum(digits(n,3)%2))/2; \\ _Kevin Ryde_, Apr 23 2021 %Y A189674 Cf. A189673. %K A189674 nonn %O A189674 1,4 %A A189674 _Clark Kimberling_, Apr 25 2011