%I
%S 1,3,23,11,47,41,50,100,123,90,174,112,179,172,201,233,168,146,211,
%T 280,247,330,294,369,411,390,401,451,374,344,448,468,516,501,536,559,
%U 574,498,523,577,662,678,722,618,615,833,686,782,717,794,707
%N Smallest k such that 3^k has exactly n 7's in its decimal representation.
%t a = {}; Do[k = 1; While[ Count[ IntegerDigits[3^k], 7] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%K base,nonn
%O 0,2
%A _Robert G. Wilson v_, Aug 10 2001
%E Name corrected by _Jon E. Schoenfield_, Jun 26 2018
