login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A130693 Powers of 2 whose digits are powers of 2. 2
1, 2, 4, 8, 128 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

It is unknown if there are any other powers of 2 with this property (that is, the digits are composed only of the numbers 1,2,4,8).

No more powers of 2 with this property up to 2^(70000) (Saunders, J. of Recreational Mathematics, v. 26, p. 151). - Emeric Deutsch, Jul 15 2007

By looking at just the lowest 20 digits of the powers of 2, the Mathematica program shows that there are no other terms less than 2^10000000. - T. D. Noe, Apr 05 2008

REFERENCES

David Wells, "The Penguin Dictionary of Curious and Interesting Numbers" (1997), p. 123.

LINKS

Table of n, a(n) for n=1..5.

MAPLE

a := proc (n) if `subset`(convert(convert(2^n, base, 10), set), {1, 2, 4, 8}) then 2^n else end if end proc: seq(a(n), n = 0 .. 300); # Emeric Deutsch, Jul 15 2007

MATHEMATICA

pwr=1; Do[pwr=Mod[2*pwr, 10^20]; d=Union[IntegerDigits[pwr]]; If[Intersection[d, {3, 5, 6, 7, 9, 0}]=={}, Print[n]], {n, 10000000}] (* T. D. Noe, Apr 05 2008 *)

CROSSREFS

Sequence in context: A018713 A007633 A018777 * A286523 A060815 A200758

Adjacent sequences:  A130690 A130691 A130692 * A130694 A130695 A130696

KEYWORD

nonn,base

AUTHOR

Greg Dresden, Jul 09 2007

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 27 08:39 EDT 2021. Contains 347689 sequences. (Running on oeis4.)