%I #9 Jun 26 2018 19:10:14
%S 1,2,13,18,22,28,43,46,71,66,83,104,86,128,127,125,139,142,124,190,
%T 195,185,202,216,215,265,235,245,244,263,278,282,274,277,286,310,320,
%U 323,432,348,376,448,400,392,459,446,441,413,587,456,486
%N Smallest k such that 7^k has exactly n 9's in its decimal representation.
%t a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 9] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%t With[{sev=Table[DigitCount[7^n,10,9],{n,600}]},Table[Position[sev,i,{1},1],{i,0,50}]]//Flatten (* _Harvey P. Dale_, May 04 2016 *)
%K base,nonn
%O 0,2
%A _Robert G. Wilson v_, Aug 10 2001
%E Name corrected by _Jon E. Schoenfield_, Jun 26 2018
