A063554 Smallest k such that 2^k has exactly n 9's in its decimal representation.

1, 12, 34, 32, 83, 53, 92, 139, 93, 172, 173, 244, 254, 335, 342, 332, 333, 415, 356, 434, 506, 473, 477, 476, 517, 532, 596, 643, 662, 673, 731, 729, 603, 735, 850, 793, 792, 966, 959, 961, 1043, 1129, 1131, 1159, 1153, 1077, 1157, 1241, 1078, 1328

Offset

0,2

Links

Table of n, a(n) for n=0..49.

Mathematica

a = {}; Do[k = 1; While[ Count[ IntegerDigits[2^k], 9] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
n9[n_]:=Module[{k=1}, While[DigitCount[2^k, 10, 9]!=n, k++]; k]; Array[n9, 50, 0] (* Harvey P. Dale, Dec 17 2011 *)
With[{t=DigitCount[#, 10, 9]&/@(2^Range[1500])}, Flatten[Table[Position[t, n, {1}, 1], {n, 0, 50}]]] (* Harvey P. Dale, Mar 17 2016 *)

Prog

(PARI) a(n)={my(k=1); while(n<>#select(d->d==9, digits(2^k)), k++); k} \\ Andrew Howroyd, Jun 26 2018

Crossrefs

Cf. A063115, A063426, A063429, A063430, A063526, A063540, A063552, A063553.

Sequence in context: A043941 A117476 A122436 * A059805 A141694 A228595

Adjacent sequences: A063551 A063552 A063553 * A063555 A063556 A063557

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 25 2018

Status

approved