OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[4^k], 9] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{n9s=DigitCount[#, 10, 9]&/@(4^Range[700])}, Flatten[Table[ Position[ n9s, n, {1}, 1], {n, 0, 50}]]] (* Harvey P. Dale, Oct 20 2013 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved