A063609 - OEIS

A063609

Smallest k such that 7^k has exactly n 3's in its decimal representation.

1, 12, 3, 17, 16, 46, 27, 42, 45, 68, 91, 105, 88, 123, 111, 101, 137, 143, 151, 127, 167, 202, 217, 193, 218, 246, 238, 207, 253, 275, 235, 251, 344, 279, 347, 335, 283, 323, 378, 361, 418, 389, 421, 384, 385, 454, 471, 436, 410, 544, 522

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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], 3] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a

With[{s=7^Range[600]}, IntegerExponent[#, 7]&/@Table[SelectFirst[s, DigitCount[ #, 10, 3]==n&], {n, 0, 50}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 21 2016 *)

CROSSREFS

Sequence in context: A268592 A127146 A306536 * A040139 A317312 A112033

Adjacent sequences: A063606 A063607 A063608 * A063610 A063611 A063612

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Aug 10 2001

EXTENSIONS

Definition clarified by Harvey P. Dale, Aug 21 2016

STATUS

approved