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A063430 Smallest k such that 2^k has exactly n 4's in its decimal representation. 9
1, 2, 18, 22, 64, 91, 117, 111, 164, 138, 182, 233, 219, 253, 343, 266, 264, 321, 315, 331, 450, 349, 451, 469, 553, 504, 510, 687, 592, 630, 710, 744, 808, 767, 828, 889, 722, 951, 789, 942, 918, 964, 1066, 1033, 890, 1183, 1263, 1171, 1229, 1130, 1291 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..150

MATHEMATICA

a = {}; Do[k = 1; While[ Count[ IntegerDigits[2^k], 4] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a

PROG

(PARI) a(n)={my(k=1); while(n<>#select(d->d==4, digits(2^k)), k++); k} \\ Harry J. Smith, Aug 20 2009, Andrew Howroyd, Jun 26 2018

CROSSREFS

Cf. A063115, A063426, A063429, A063526, A063540, A063552, A063553, A063554.

Sequence in context: A247457 A015787 A322489 * A031104 A115042 A191461

Adjacent sequences:  A063427 A063428 A063429 * A063431 A063432 A063433

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Aug 10 2001

EXTENSIONS

Name corrected by Jon E. Schoenfield, Jun 25 2018

STATUS

approved

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Last modified August 25 11:01 EDT 2019. Contains 326324 sequences. (Running on oeis4.)