A063610 - OEIS

A063610

Smallest k such that 7^k has exactly n 4's in its decimal representation.

1, 2, 10, 15, 26, 32, 33, 58, 62, 50, 46, 89, 102, 108, 90, 118, 130, 122, 146, 144, 112, 138, 196, 224, 226, 212, 256, 250, 259, 239, 218, 254, 386, 260, 318, 292, 353, 321, 358, 326, 392, 401, 330, 396, 427, 442, 438, 443, 450, 449, 474

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OFFSET

0,2

LINKS

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

MATHEMATICA

a = {}; Do[k = 1; While[ Count[ IntegerDigits[7^k], 4] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a

Module[{nn=50, p7s}, p7s=Table[DigitCount[7^n, 10, 4], {n, 20nn}]; Join[{1}, Table[ Position[p7s, i, {1}, 1], {i, nn}]]]//Flatten (* Harvey P. Dale, Jun 13 2016 *)

CROSSREFS

Sequence in context: A272041 A212160 A134861 * A369650 A181474 A047187

Adjacent sequences: A063607 A063608 A063609 * A063611 A063612 A063613

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Aug 10 2001

EXTENSIONS

Name corrected by Jon E. Schoenfield, Jun 26 2018

STATUS

approved