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%I #17 Jul 18 2021 04:27:50
%S 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 16,16,17,17,17,18,18,18,19,20,20,21,21,21,22,23,23,24,25,25,26,26,26,
%U 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 Partial sums of A156595.
%C See A156595.
%H Andrew Howroyd, <a href="/A189717/b189717.txt">Table of n, a(n) for n = 1..10000</a>
%H Kevin Ryde, <a href="http://user42.tuxfamily.org/terdragon/index.html">Iterations of the Terdragon Curve</a>, see index "AltTurnsR".
%F a(n) = floor((n+1)/3) + floor(n/3) - a(floor(n/3)), with a(0) = 0.
%t (See A189715.)
%o (PARI) a(n) = {if(n<=0, 0, (n+1)\3 + n\3 - a(n\3))} \\ _Andrew Howroyd_, Sep 10 2019
%o (PARI) a(n) = (n - subst(Pol(digits(n,3)%2),'x,-1))/2; \\ _Kevin Ryde_, Jul 18 2021
%Y Cf. A156595, A189715, A189716.
%K nonn
%O 1,3
%A _Clark Kimberling_, Apr 26 2011
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