%I #9 Jun 01 2021 10:29:53
%S 5,10,15,20,22,23,40,41,43,60,61,62,85,170,255,320,325,330,335,340,
%T 342,343,352,357,362,367,368,373,378,383,640,645,650,655,656,661,666,
%U 671,680,681,683,688,693,698,703,960,965,970,975
%N Base-4 run lengths alternate: even, odd, even,...
%H Harvey P. Dale, <a href="/A044890/b044890.txt">Table of n, a(n) for n = 1..1000</a>
%t eoe4Q[n_]:=Module[{c=If[EvenQ[Length[#]],1,0]&/@Split[ IntegerDigits[ n,4]]},c==PadRight[{},Length[c],{1,0}]]; Select[Range[1000],eoe4Q] (* _Harvey P. Dale_, Jun 01 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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