A063615 Smallest k such that 7^k has exactly n 9's in its decimal representation.

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

Links

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

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

Adjacent sequences: A063612 A063613 A063614 * A063616 A063617 A063618

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 26 2018

Status

approved