整数問題bot/Nederpeltについて、ここに記述してください。


We  can  express a_k_, as  a_k=  2^k-1^a_1 +  e(2^k-1^-1).
  According to  Fermat's little theorem, 
    if k =  a_1 >  2,  then a_1 divides a_k.
  This means that for  a_1 > 2 the length A of a prime chain cannot exceed a_1—1
   (Nederpelt et  al.  [7]). 

Actually, most of the prime chains are  considerably shorter. 
It  is not  known whether arbitrarily longchains exist.

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Fermat's little theorem
　2**(k-1) = 1 (mod k)  {k > 2)