%I #9 Mar 30 2012 17:20:41
%S 63,127,191,207,223,239,243,247,251,252,253,254,319,383,447,463,479,
%T 495,499,503,507,508,509,510,575,639,703,719,735,751,755,759,763,764,
%U 765,766,783,799,815,819,823,827,828,829,830
%N Numbers with exactly 3 3's in base 4 expansion.
%H Harvey P. Dale, <a href="/A023720/b023720.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[ Range[ 864 ], (Count[ IntegerDigits[ #, 4 ], 3 ]==3)& ]
%K nonn,base,easy
%O 1,1
%A _Olivier GĂ©rard_