[seqfan] Numbers of the Form 2^j (mod 10^k)

[Paul D. Hanna]

The statements below need correction (from prior email).
 
The final digits (5 digits in the example) that are given of the unknown
integer N, 
are not to begin with leading zeros. 
  
And the sequence of numbers of the form 2^j (mod 10^k) 
will not list numbers with leading zeros, like 008 for example. 
These numbers will be listed elsewhere, such as 1008. 
 
And, obviously, I should have typed a '5' for the power of 10, not '6',
when I said:
"That is, which 5-digit numbers are of the form: 
    2^j (mod 10^5) 
where j is any positive integer?"
 
Sorry to trouble you, should you find these matters trivial.
    Paul
 
On Fri, 27 Aug 2004 11:19:49 -0400 "Paul D. Hanna" <pauldhanna at juno.com>
writes:
     Given only the last 5 (say) digits of a large integer N, 
how can you determine if N is NOT some power of 2? 
That is, which 5-digit numbers are of the form: 
    2^j (mod 10^6) 
where j is any positive integer? 
So, if the last 5 digits of N were not in this sequence, 
then N would not be a power of 2. 
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