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A110581
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Primes p such that 2p-1 is prime, but 4p-3 is not prime.
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1
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3, 7, 31, 37, 97, 139, 157, 199, 211, 229, 271, 307, 337, 367, 379, 547, 577, 601, 607, 661, 691, 727, 811, 877, 937, 967, 997, 1009, 1171, 1237, 1297, 1399, 1429, 1459, 1609, 1627, 1657, 1759, 1867, 2011, 2029, 2137, 2221, 2281, 2467, 2539, 2551, 2557
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A subsequence of A005382, primes p such that 2p-1 is also prime. Note that for all n, 2a(n)-1 is not in this sequence.
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REFERENCES
| Jeffrey J. Holt, The minimal number of solutions to phi(n)=phi(n+k), Math. Comp., 72 (2003), 2059-2061.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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MATHEMATICA
| Select[Prime[Range[2, 1000]], PrimeQ[2#-1] && !PrimeQ[4#-3]&]
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CROSSREFS
| Sequence in context: A138862 A080173 A023266 * A128436 A034915 A145479
Adjacent sequences: A110578 A110579 A110580 * A110582 A110583 A110584
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KEYWORD
| nonn
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Jul 28 2005
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