A063526 Smallest k such that 2^k has exactly n 5's in its decimal representation.

1, 8, 16, 39, 41, 68, 131, 108, 142, 178, 198, 201, 167, 215, 283, 344, 367, 318, 404, 428, 312, 461, 441, 556, 506, 562, 536, 716, 652, 679, 733, 690, 575, 807, 627, 949, 811, 867, 932, 1035, 1003, 1088, 893, 1112, 1193, 1080, 1127, 1094, 1016, 1283

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], 5] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Join[{1}, Flatten[With[{pwrs=DigitCount[#, 10, 5]&/@(2^Range[0, 1300])}, Table[Position[pwrs, n, 1, 1], {n, 50}]]]-1] (* Harvey P. Dale, Jan 28 2013 *)

Prog

(PARI) a(n)={my(k=1); while(n<>#select(d->d==5, digits(2^k)), k++); k} \\ Harry J. Smith, Aug 25 2009, Andrew Howroyd, Jun 26 2018

Crossrefs

Cf. A063115, A063426, A063429, A063430, A063540, A063552, A063553, A063554.

Sequence in context: A054301 A197773 A057584 * A156331 A269513 A024700

Adjacent sequences: A063523 A063524 A063525 * A063527 A063528 A063529

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 25 2018

Status

approved