A131542 Least power of 2 having exactly n consecutive 8's in its decimal representation.

3, 19, 39, 180, 316, 971, 6836, 25263, 103825, 279274, 279268, 1727604, 18053496, 8760852

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)=39 because 2^39(i.e. 549755813888) is the smallest power of 2 to contain a run of 3 consecutive eights in its decimal form.

Mathematica

a = ""; Do[ a = StringJoin[a, "8"]; b = StringJoin[a, "8"]; k = 1; While[ StringPosition[ ToString[2^k], a] == {} || StringPosition[ ToString[2^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]

Crossrefs

Sequence in context: A117674 A114704 A167053 * A227878 A042371 A141644

Adjacent sequences: A131539 A131540 A131541 * A131543 A131544 A131545

Keyword

more,nonn,base

Author

Shyam Sunder Gupta, Aug 26 2007

Extensions

Two more terms from Sean A. Irvine, May 31 2010

a(13)-a(14) from Lars Blomberg, Jan 24 2013

Status

approved