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A058340
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Primes p such that phi(x) = p-1 has only 2 solutions, namely x = p and x = 2p.
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3
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11, 23, 29, 31, 47, 53, 59, 67, 71, 79, 83, 103, 107, 127, 131, 137, 139, 149, 151, 167, 173, 179, 191, 197, 199, 211, 223, 227, 229, 239, 251, 263, 269, 271, 283, 293, 307, 311, 317, 331, 347, 359, 367, 373, 379, 383, 389, 419, 431, 439, 443, 463, 467, 479
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Two solutions, p and 2p, exist for all odd primes p; primes in sequence have no other solutions.
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EXAMPLE
| For p=2, Phi[x]=1 has only two solutions, but they are 1 and 2, not 2 and 4, so 2 is not in the sequence.
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CROSSREFS
| Cf. A000010, A006093, A000040, A066071-A066080, A138537.
Sequence in context: A090423 A086102 * A138537 A136000 A054723 A109981
Adjacent sequences: A058337 A058338 A058339 * A058341 A058342 A058343
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Dec 14 2000
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EXTENSIONS
| Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 06 2008
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