A131543 Least power of 2 having exactly n consecutive 9's in its decimal representation.

12, 33, 50, 421, 422, 2187, 15554, 42483, 42485, 42486, 1522085, 2662514, 6855863, 6855865

Offset

1,1

Comments

No more terms < 28*10^6.

Links

Table of n, a(n) for n=1..14.

Popular Computing (Calabasas, CA), Two Tables, Vol. 1, (No. 9, Dec 1973), page PC9-16.

Example

a(3)=50 because 2^50(i.e. 1125899906842624) is the smallest power of 2 to contain a run of 3 consecutive nines in its decimal form.

Mathematica

a = ""; Do[ a = StringJoin[a, "9"]; b = StringJoin[a, "9"]; k = 1; While[ StringPosition[ ToString[2^k], a] == {} || StringPosition[ ToString[2^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]

Crossrefs

Sequence in context: A050690 A079561 A328326 * A372026 A063296 A372027

Adjacent sequences: A131540 A131541 A131542 * A131544 A131545 A131546

Keyword

more,nonn,base

Author

Shyam Sunder Gupta, Aug 26 2007

Extensions

a(11) from Sean A. Irvine, May 31 2010

a(12)-a(14) from Lars Blomberg, Jan 24 2013

Status

approved