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Numbers whose base-7 representation has an even number of runs.
3

%I #10 Jun 18 2021 20:45:05

%S 7,9,10,11,12,13,14,15,17,18,19,20,21,22,23,25,26,27,28,29,30,31,33,

%T 34,35,36,37,38,39,41,42,43,44,45,46,47,49,56,58,59,60,61,62,65,73,81,

%U 89,97,98,106,112,113,115,116,117,118,122,130

%N Numbers whose base-7 representation has an even number of runs.

%t Select[Range[200],EvenQ[Length[Split[IntegerDigits[#,7]]]]&] (* _Harvey P. Dale_, Nov 17 2013 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_