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A063606 Smallest k >= 0 such that 7^k has exactly n 0's in its decimal representation. 9
0, 4, 9, 13, 25, 55, 39, 41, 45, 70, 69, 65, 75, 107, 109, 134, 167, 142, 156, 196, 157, 205, 214, 180, 213, 183, 162, 251, 263, 276, 268, 290, 306, 295, 369, 313, 332, 293, 353, 340, 357, 387, 367, 476, 334, 509, 363, 474, 454, 488, 453 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

MATHEMATICA

a = {}; Do[k = 0; While[ Count[ IntegerDigits[7^k], 0] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a

PROG

(PARI) A063606(n)=for(k=n, oo, #select(d->!d, digits(5^k))==n&&return(k)) \\ M. F. Hasler, Jun 14 2018

CROSSREFS

Cf. A031146 (analog for 2^k), A063555 (analog for 3^k), A063575 (analog for 4^k), A063585 (for 5^k), A063596 (analog for 6^k).

Sequence in context: A257337 A056227 A048261 * A033287 A041323 A319217

Adjacent sequences:  A063603 A063604 A063605 * A063607 A063608 A063609

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Aug 10 2001

STATUS

approved

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Last modified January 17 18:08 EST 2020. Contains 330987 sequences. (Running on oeis4.)