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Numbers whose base-7 representation has the same number of 2's and 5's.
1

%I #11 Jun 20 2021 08:36:42

%S 0,1,3,4,6,7,8,10,11,13,19,21,22,24,25,27,28,29,31,32,34,37,42,43,45,

%T 46,48,49,50,52,53,55,56,57,59,60,62,68,70,71,73,74,76,77,78,80,81,83,

%U 86,91,92,94,95,97,103,110,124,131,133,134,136,137,139,145,147,148

%N Numbers whose base-7 representation has the same number of 2's and 5's.

%H Harvey P. Dale, <a href="/A039042/b039042.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[0,200],DigitCount[#,7,2]==DigitCount[#,7,5]&] (* _Harvey P. Dale_, Dec 19 2016 *)

%K nonn,base,easy

%O 1,3

%A _Olivier GĂ©rard_