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A063580
Smallest k such that 4^k has exactly n 5's in its decimal representation.
1
1, 4, 8, 37, 38, 34, 72, 54, 71, 89, 99, 136, 105, 134, 151, 172, 206, 159, 202, 214, 156, 304, 274, 278, 253, 281, 268, 358, 326, 375, 389, 345, 424, 429, 460, 488, 449, 484, 466, 521, 531, 544, 568, 556, 638, 540, 590, 547, 508, 677, 606
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
Sequence in context: A047710 A370573 A335991 * A003049 A098563 A231398
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved