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%I #11 Apr 24 2021 03:27:46
%S 0,0,1,1,1,2,3,3,4,4,4,5,5,5,6,7,7,8,9,9,10,10,10,11,12,12,13,13,13,
%T 14,14,14,15,16,16,17,17,17,18,18,18,19,20,20,21,22,22,23,23,23,24,25,
%U 25,26,27,27,28,28,28,29,30,30,31,31,31,32,32,32,33,34,34,35,36,36,37,37,37,38,39,39,40
%N Partial sums of A189640.
%C See A189640.
%F a(n) = a(floor((n+2)/3)) + floor(n/3), where a(1)=0.
%t (See A189640.)
%o (PARI) a(n) = n--; (n - vecsum(digits(n,3)%2))/2; \\ _Kevin Ryde_, Apr 23 2021
%Y Cf. A189640, A189672 (essentially the same).
%K nonn
%O 1,6
%A _Clark Kimberling_, Apr 24 2011