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Search: id:A087693
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| A087693 |
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Lesser twin prime p such that 2^p-1 is composite. |
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+0
1
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| 11, 29, 41, 59, 71, 101, 137, 149, 179, 191, 197, 227, 239, 269, 281, 311, 347, 419, 431, 461, 569, 599, 617, 641, 659, 809, 821, 827, 857, 881, 1019, 1031, 1049, 1061, 1091, 1151, 1229, 1277, 1289, 1301, 1319, 1427, 1451, 1481, 1487, 1607, 1619, 1667, 1697
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Look at all twin primes (p1, p2); if 2^p1 - 1 is composite print p2.
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PROGRAM
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(PARI) twopm1(n) = { forprime(x=2, n, y=2^x-1; if(!isprime(y) && isprime(x+2), print1(x", ") ) ) }
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CROSSREFS
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Sequence in context: A153768 A092194 A134307 this_sequence A106017 A106065 A156110
Adjacent sequences: A087690 A087691 A087692 this_sequence A087694 A087695 A087696
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Oct 25 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 07 2003
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