%I A140452
%S A140452 11,22,23,25,28,29,33
%N A140452 2^(a(n))-1 contains an overpseudoprime divisor.
%C A140452 If p is a prime then p is in the sequence iff 2^p-1 is a composite number.
%D A140452 V. Shevelev, Overpsudoprimes, Mersenne Numbers and Wieferich Primes, 
               http://arxiv.org/abs/0806.3412
%Y A140452 Cf. A141232, A137576, A005420, A049479.
%Y A140452 Sequence in context: A138838 A139337 A040110 this_sequence A048136 A166713 
               A095779
%Y A140452 Adjacent sequences: A140449 A140450 A140451 this_sequence A140453 A140454 
               A140455
%K A140452 nonn
%O A140452 1,1
%A A140452 Vladimir Shevelev (shevelev(AT)bgu.ac.il), Jun 26 2008