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%I #13 Jun 26 2018 19:20:02
%S 1,2,8,18,30,50,36,64,62,104,96,133,98,115,111,110,150,193,191,242,
%T 189,288,224,253,292,308,318,254,303,331,414,389,405,373,479,436,425,
%U 504,537,499,523,543,498,600,546,584,643,640,656,626,663
%N Smallest k such that 4^k has exactly n 6's in its decimal representation.
%H Vincenzo Librandi, <a href="/A063581/b063581.txt">Table of n, a(n) for n = 0..200</a>
%t a = {}; Do[k = 1; While[ Count[ IntegerDigits[4^k], 6] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%t Log[4,#]&/@Table[First[Select[4^Range[900],DigitCount[#,10,6]==n&]], {n,0,60}] (* _Harvey P. Dale_, May 15 2011 *)
%K base,nonn
%O 0,2
%A _Robert G. Wilson v_, Aug 10 2001
%E Name corrected by _Jon E. Schoenfield_, Jun 26 2018
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