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Search: id:A087699
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| A087699 |
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Greater twin prime p such that 2^p-1 is composite. |
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+0
1
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| 43, 73, 103, 109, 139, 151, 181, 193, 199, 229, 241, 271, 283, 313, 349, 421, 433, 463, 523, 571, 601, 619, 643, 661, 811, 823, 829, 859, 883, 1021, 1033, 1051, 1063, 1093, 1153, 1231, 1291, 1303, 1321, 1429, 1453, 1483, 1489, 1609, 1621, 1669, 1699, 1723
(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^p2 - 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: A139875 A087765 A141971 this_sequence A054807 A139932 A080177
Adjacent sequences: A087696 A087697 A087698 this_sequence A087700 A087701 A087702
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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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Corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 07 2003
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