OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 2] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{pwrs=7^Range[600]}, Log[7, #]&/@Table[SelectFirst[pwrs, DigitCount[ #, 10, 2] == n&], {n, 0, 50}]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, Aug 25 2015 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved