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Old 2019-04-10, 14:17   #1
Mar 2018

10000011112 Posts
Default for which values of p this expression has the form s*2^k?

let be p an arbitrary prime...
can you find values of p such that

(10^p-1)/9+1 has the form s*2^k?

where s is a prime and k an integer >0

example p=3 does the job
infact (10^3-1)/9+1 has the form 7*2^4

p=5 does not the job because

(10^5-1)/9+1 has the form 2^3*3*463...
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