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Numbers whose base-9 representation has the same number of 7's and 8's.
1

%I #15 Nov 03 2024 19:20:52

%S 0,1,2,3,4,5,6,9,10,11,12,13,14,15,18,19,20,21,22,23,24,27,28,29,30,

%T 31,32,33,36,37,38,39,40,41,42,45,46,47,48,49,50,51,54,55,56,57,58,59,

%U 60,71,79,81,82,83,84,85,86,87,90,91,92,93,94,95,96,99,100,101,102

%N Numbers whose base-9 representation has the same number of 7's and 8's.

%t okQ[n_]:=Module[{idn9=IntegerDigits[n,9]},Count[idn9,7]==Count[idn9,8]]

%t Select[Range[0,110],okQ] (* _Harvey P. Dale_, Dec 14 2010 *)

%t Select[Range[0,120],DigitCount[#,9,7]==DigitCount[#,9,8]&] (* _Harvey P. Dale_, Nov 03 2024 *)

%Y Cf. A007095.

%K nonn,base,easy

%O 1,3

%A _Olivier GĂ©rard_