%I A086252
%S A086252 2,11,29,92,113,223,295,333,397
%N A086252 a(n) is the smallest k such that 2^k-1 has n primitive prime factors.
%C A086252 A prime factor of 2^n-1 is called primitive if it does not divide 2^r-1 
               for any r<n. Equivalently, p is a primitive prime factor of 2^n-1 
               if ord(2,p)=n. See A086251 for the number of primitive prime factors 
               in 2^n-1.
%C A086252 No more terms < 673. (2^673-1 is the first that is not completely factored 
               in the linked reference.) - David Wasserman (wasserma(AT)spawar.navy.mil), 
               Feb 22 2005
%D A086252 J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, 
               Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H A086252 J. Brillhart et al., Factorizations of b^n +- 1 <a href="http://www.ams.org/
               online_bks/conm22/">Available on-line</a>
%e A086252 a(2) = 11 because 2^11-1 = 23*89, both 23 and 89 have order 11 and the 
               numbers 2^r-1 have only 0 or 1 primitive prime factors.
%Y A086252 Cf. A086251.
%Y A086252 Sequence in context: A009312 A154251 A092275 this_sequence A106926 A133558 
               A140745
%Y A086252 Adjacent sequences: A086249 A086250 A086251 this_sequence A086253 A086254 
               A086255
%K A086252 hard,more,nonn
%O A086252 1,1
%A A086252 T. D. Noe (noe(AT)sspectra.com), Jul 14 2003
%E A086252 More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 22 
               2005