A063611 Smallest k such that 7^k has exactly n 5's in its decimal representation.

1, 7, 15, 27, 21, 49, 55, 47, 51, 87, 85, 107, 75, 99, 61, 149, 138, 133, 171, 135, 165, 237, 209, 197, 269, 221, 232, 219, 277, 248, 258, 306, 271, 264, 357, 296, 310, 347, 354, 260, 342, 374, 407, 425, 362, 457, 485, 480, 486, 488, 492

Offset

0,2

Links

Table of n, a(n) for n=0..50.

Mathematica

a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Join[{1}, With[{p7=7^Range[0, 500]}, Flatten[Table[Position[p7, _?(DigitCount[ #, 10, 5]==n&), {1}, 1], {n, 50}]]-1]] (* Harvey P. Dale, Sep 17 2013 *)

Crossrefs

Sequence in context: A154935 A012480 A226470 * A292379 A146624 A239934

Adjacent sequences: A063608 A063609 A063610 * A063612 A063613 A063614

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 26 2018

Status

approved