login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A045875 a(n) is the smallest m for which the decimal representation of 2^m contains n consecutive identical digits. 26
0, 16, 24, 41, 220, 971, 972, 8554, 42485, 42486, 271979, 1039315, 1727602, 6855865, 63416789, 106892452 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Next term is greater than 20000. - David Wasserman, Feb 16 2002
a(11) > 250000. - Robert G. Wilson v, Oct 21 2010
a(15) > 10297974. - T. D. Noe, Sep 08 2012
a(17) > 107000000. - Paul Geneau de Lamarlière, Feb 04 2024
LINKS
MATHEMATICA
a[n_] := Block[{k = 0}, While[ !MemberQ[ Length /@ Split@ IntegerDigits[2^k], n], k++ ]; k]; Table[a[n], {n, 6}] (* Robert G. Wilson v, Oct 21 2010 *)
PROG
(Python)
def A045875(n):
l, x = [str(d)*n for d in range(10)], 1
for m in range(10**9):
s = str(x)
for k in l:
if k in s:
return m
x *= 2
return 'search limit reached'
# Chai Wah Wu, Dec 17 2014
CROSSREFS
Cf. A215732 (the digits).
Sequence in context: A110228 A269519 A175161 * A046434 A111046 A205187
KEYWORD
base,nonn,hard,more
AUTHOR
EXTENSIONS
More terms from David Wasserman, Feb 16 2002
a(9) and a(10) from Robert G. Wilson v, Oct 21 2010
a(11)-a(13) added by T. D. Noe, Sep 04 2012
a(14) added by T. D. Noe, Sep 06 2012
Definition clarified by Daran Gill, Mar 24 2013
a(15) from Bert Dobbelaere, Feb 25 2019
a(16) from Paul Geneau de Lamarlière, Feb 04 2024
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 18:16 EDT 2024. Contains 371916 sequences. (Running on oeis4.)