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Numbers whose base-7 representation has the same number of 2's and 4's.
1

%I #14 Jun 20 2021 15:04:42

%S 0,1,3,5,6,7,8,10,12,13,18,21,22,24,26,27,30,35,36,38,40,41,42,43,45,

%T 47,48,49,50,52,54,55,56,57,59,61,62,67,70,71,73,75,76,79,84,85,87,89,

%U 90,91,92,94,96,97,102,109,123,126,127,129,131,132,137,144,147,148

%N Numbers whose base-7 representation has the same number of 2's and 4's.

%H Daniel Starodubtsev, <a href="/A039041/b039041.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[0,200],DigitCount[#,7,2]==DigitCount[#,7,4]&] (* _Harvey P. Dale_, Dec 18 2011 *)

%Y Cf. A007093.

%K nonn,base,easy

%O 1,3

%A _Olivier GĂ©rard_