|
|
A063608
|
|
Smallest k such that 7^k has exactly n 2's in its decimal representation.
|
|
0
|
|
|
1, 4, 12, 10, 20, 32, 30, 68, 49, 73, 82, 93, 125, 103, 109, 131, 146, 119, 161, 113, 172, 163, 191, 197, 199, 240, 232, 243, 210, 217, 288, 317, 292, 289, 321, 333, 319, 327, 276, 374, 358, 397, 354, 357, 373, 452, 428, 489, 391, 516, 470
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
MATHEMATICA
|
a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 2] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{pwrs=7^Range[600]}, Log[7, #]&/@Table[SelectFirst[pwrs, DigitCount[ #, 10, 2] == n&], {n, 0, 50}]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, Aug 25 2015 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|