cp's OEIS Frontend

A189717 Partial sums of A156595.

%I A189717 #21 Feb 16 2025 01:11:20
%S A189717 0,1,2,2,3,3,3,4,4,4,5,6,6,7,7,7,8,9,9,10,11,11,12,12,12,13,14,14,15,
%T A189717 16,16,17,17,17,18,18,18,19,20,20,21,21,21,22,23,23,24,25,25,26,26,26,
%U A189717 27,27,27,28,29,29,30,30,30,31,31,31,32,33,33,34,34,34,35,36,36,37,38,38,39,39,39,40,40
%N A189717 Partial sums of A156595.
%C A189717 See A156595.
%H A189717 Andrew Howroyd, <a href="/A189717/b189717.txt">Table of n, a(n) for n = 1..10000</a>
%H A189717 Kevin Ryde, <a href="http://user42.tuxfamily.org/terdragon/index.html">Iterations of the Terdragon Curve</a>, see index "AltTurnsR".
%F A189717 a(n) = floor((n+1)/3) + floor(n/3) - a(floor(n/3)), with a(0) = 0.
%t A189717 (See A189715.)
%o A189717 (PARI) a(n) = {if(n<=0, 0, (n+1)\3 + n\3 - a(n\3))} \\ _Andrew Howroyd_, Sep 10 2019
%o A189717 (PARI) a(n) = (n - subst(Pol(digits(n,3)%2),'x,-1))/2; \\ _Kevin Ryde_, Jul 18 2021
%o A189717 (Python)
%o A189717 from sympy import integer_log
%o A189717 def A189717(n): return sum(((m:=n//9**i)-2)//9+(m-3)//9+(m-5)//9+(m-8)//9+4 for i in range(integer_log(n,9)[0]+1)) # _Chai Wah Wu_, Feb 15 2025
%Y A189717 Cf. A156595, A189715, A189716.
%K A189717 nonn
%O A189717 1,3
%A A189717 _Clark Kimberling_, Apr 26 2011