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A163325 Pick digits at the even distance from the least significant end of the ternary expansion of n, then convert back to decimal.

%I A163325 #33 Sep 27 2020 02:38:32
%S A163325 0,1,2,0,1,2,0,1,2,3,4,5,3,4,5,3,4,5,6,7,8,6,7,8,6,7,8,0,1,2,0,1,2,0,
%T A163325 1,2,3,4,5,3,4,5,3,4,5,6,7,8,6,7,8,6,7,8,0,1,2,0,1,2,0,1,2,3,4,5,3,4,
%U A163325 5,3,4,5,6,7,8,6,7,8,6,7,8,9,10,11,9,10,11,9,10,11,12,13,14,12,13,14
%N A163325 Pick digits at the even distance from the least significant end of the ternary expansion of n, then convert back to decimal.
%H A163325 Antti Karttunen, <a href="/A163325/b163325.txt">Table of n, a(n) for n = 0..728</a>
%H A163325 Kevin Ryde, <a href="http://oeis.org/plot2a?name1=A163325&amp;name2=A163326&amp;tform1=untransformed&amp;tform2=untransformed&amp;shift=0&amp;radiop1=xy&amp;drawpoints=true&amp;drawlines=true">Plot2 of X=A163325,Y=A163326</a>, illustrating the ternary Z-order curve.
%H A163325 <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a>
%F A163325 a(0) = 0, a(n) = (n mod 3) + 3*a(floor(n/9)).
%F A163325 a(n) = Sum_{k>=0} {A030341(n,k)*b(k)} where b is the sequence (1,0,3,0,9,0,27,0,81,0,243,0... = A254006): powers of 3 alternating with zeros. - _Philippe Deléham_, Oct 22 2011
%F A163325 A037314(a(n)) + 3*A037314(A163326(n)) = n for all n.
%e A163325 11 in ternary base (A007089) is written as '102' (1*9 + 0*3 + 2), from which we pick the "zeroth" and 2nd digits from the right, giving '12' = 1*3 + 2 = 5, thus a(11) = 5.
%o A163325 (PARI) a(n) = fromdigits(digits(n,9)%3,3); \\ _Kevin Ryde_, May 14 2020
%Y A163325 A059905 is an analogous sequence for binary.
%Y A163325 Cf. A007089, A163327, A163328, A163329.
%K A163325 nonn,base,look
%O A163325 0,3
%A A163325 _Antti Karttunen_, Jul 29 2009
%E A163325 Edited by _Charles R Greathouse IV_, Nov 01 2009