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%I #20 Sep 27 2020 02:38:05
%S 0,0,0,1,1,1,2,2,2,0,0,0,1,1,1,2,2,2,0,0,0,1,1,1,2,2,2,3,3,3,4,4,4,5,
%T 5,5,3,3,3,4,4,4,5,5,5,3,3,3,4,4,4,5,5,5,6,6,6,7,7,7,8,8,8,6,6,6,7,7,
%U 7,8,8,8,6,6,6,7,7,7,8,8,8,0,0,0,1,1,1,2,2,2,0,0,0,1,1,1,2,2,2,0,0,0
%N Pick digits at the odd distance from the least significant end of the ternary expansion of n, then convert back to decimal.
%H Antti Karttunen, <a href="/A163326/b163326.txt">Table of n, a(n) for n = 0..728</a>
%H Kevin Ryde, <a href="http://oeis.org/plot2a?name1=A163325&name2=A163326&tform1=untransformed&tform2=untransformed&shift=0&radiop1=xy&drawpoints=true&drawlines=true">Plot2 of X=A163325,Y=A163326</a>, illustrating the ternary Z-order curve.
%H <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a>
%F a(n) = A163325(floor(n/3))
%F a(n) = Sum_{k>=0} A030341(n,k)*b(k) with (b) = (0,1,0,3,0,9,0,27,0,81,0,243,0,...): powers of 3 alternating with zeros. - _Philippe Deléham_, Oct 22 2011
%e 42 in ternary base (A007089) is written as '1120' (1*27 + 1*9 + 2*3 + 0), from which we pick the first and 3rd digits from the right (zero-based!), giving '12' = 1*3 + 2 = 5, thus a(42) = 5.
%o (PARI) a(n) = fromdigits(digits(n,9)\3,3); \\ _Kevin Ryde_, May 15 2020
%Y A059906 is an analogous sequence for binary. Note that A037314(A163325(n)) + 3*A037314(A163326(n)) = n for all n. Cf. A007089, A163327-A163329.
%K nonn,base
%O 0,7
%A _Antti Karttunen_, Jul 29 2009
%E Edited by _Charles R Greathouse IV_, Nov 01 2009
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