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%I #15 Apr 21 2021 04:23:44
%S 1,2,9,13,17,18,22,26,28,29,51,52,55,56,66,68,81,117,121,125,161,162,
%T 202,234,238,242,244,245,252,256,260,261,265,269,352,353,375,376,459,
%U 463,467,468,472,476,483,484,487,488,495,499
%N Numbers whose base-3 run lengths alternate: odd, even, odd, ...
%H Harvey P. Dale, <a href="/A044904/b044904.txt">Table of n, a(n) for n = 1..1000</a>
%t b3rQ[n_]:=Module[{r=Boole[OddQ/@(Length/@Split[IntegerDigits[ n,3]])]},r == PadRight[{},Length[r],{1,0}]]; Select[Range[500],b3rQ] (* _Harvey P. Dale_, Jul 17 2020 *)
%Y Cf. A007089.
%K nonn,base
%O 1,2
%A _Clark Kimberling_
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