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A063615
Smallest k such that 7^k has exactly n 9's in its decimal representation.
0
1, 2, 13, 18, 22, 28, 43, 46, 71, 66, 83, 104, 86, 128, 127, 125, 139, 142, 124, 190, 195, 185, 202, 216, 215, 265, 235, 245, 244, 263, 278, 282, 274, 277, 286, 310, 320, 323, 432, 348, 376, 448, 400, 392, 459, 446, 441, 413, 587, 456, 486
OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 9] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{sev=Table[DigitCount[7^n, 10, 9], {n, 600}]}, Table[Position[sev, i, {1}, 1], {i, 0, 50}]]//Flatten (* Harvey P. Dale, May 04 2016 *)
CROSSREFS
Sequence in context: A067522 A128852 A191765 * A297837 A246358 A262688
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved