OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[4^k], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{c=4^Range[700]}, Flatten[IntegerExponent[#, 4]&/@Table[Select[c, DigitCount[#, 10, 5] == n&, 1], {n, 0, 50}]]] (* Harvey P. Dale, Nov 06 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