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A063631
Smallest k such that 9^k has exactly n 5's in its decimal representation.
0
1, 4, 13, 23, 20, 46, 52, 35, 37, 68, 80, 103, 106, 91, 115, 138, 123, 148, 152, 137, 166, 170, 156, 199, 182, 188, 222, 225, 237, 200, 294, 292, 247, 288, 272, 289, 278, 314, 327, 328, 402, 363, 269, 312, 374, 413, 372, 407, 399, 444, 411
OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[9^k], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{p9=Table[{n, 9^n}, {n, 450}]}, Transpose[Table[SelectFirst[p9, DigitCount[ #[[2]], 10, 5]==i&], {i, 0, 50}]][[1]]] (* Harvey P. Dale, Nov 12 2015 *)
CROSSREFS
Sequence in context: A339804 A256390 A264623 * A031240 A031320 A112263
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved