%I #9 Jul 16 2017 13:19:56
%S 21,42,63,64,84,86,87,106,127,128,149,168,169,171,191,192,213,234,252,
%T 253,254,257,258,259,277,298,319,320,336,337,338,339,344,345,346,347,
%U 348,349,350,351,362,383,384,405,424,425,427
%N Numbers whose maximal base 4 run length is 3.
%t Select[Range[500],Max[Length/@Split[IntegerDigits[#,4]]]==3&] (* _Harvey P. Dale_, Jul 16 2017 *)
%Y Cf. A043278.
%K nonn,base
%O 1,1
%A _Clark Kimberling_