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A140803
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Numbers of the form (2^(pq)-1) /((2^p-1)*(2^q-1)), where p>q are primes.
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1
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3, 11, 43, 151, 683, 2359, 2731, 43691, 174763, 599479, 2796203, 8727391, 9588151, 178956971, 715827883, 2454285751
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OFFSET
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1,1
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COMMENTS
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The sequence contains, in particular, A126614 (q=2) and A143012 (q=3).
If pq-1 is squarefree then the terms of the sequence are either primes or overpseudoprimes to base 2 (see A141232). In particular, they are strong pseudoprimes to base 2 (A001262).
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LINKS
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Table of n, a(n) for n=1..16.
V. Shevelev, Process of "primoverization" of numbers of the form a^n-1, arXiv:0807.2332
S. Wagstaff, Factorizations of 2^n-1
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EXAMPLE
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Entry 3 from (q=2,p=3), entry 11 from (q=2,p=5), entry 43 from (q=2,p=7), entry 151 from (q=3,p=5), entry 683 from (q=2,p=11).
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CROSSREFS
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Cf. A001262, A141232, A126614, A143012.
Sequence in context: A118166 A106876 A034477 * A084643 A007583 A026671
Adjacent sequences: A140800 A140801 A140802 * A140804 A140805 A140806
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KEYWORD
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nonn
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AUTHOR
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Vladimir Shevelev, Jul 15 2008, Jul 22 2008; corrected Sep 07 2008
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STATUS
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approved
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