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A065507
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Smallest prime q such that (p^q+1)/(p+1) is a prime, where p = prime(n).
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6
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3, 3, 5, 3, 5, 3, 7, 17, 11, 7, 109, 5, 17, 5, 5, 21943, 17, 7, 3, 5, 7, 3, 19, 13
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| It is known that for the prime 97, a(25) > 31000. - T. D. Noe (noe(AT)sspectra.com), Feb 13 2004
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LINKS
| H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
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MATHEMATICA
| Do[p = Prime[n]; k = 1; While[ !PrimeQ[ (p^Prime[k] + 1)/(p + 1)], k++ ]; Print[ Prime[k]], {n, 1, 15} ]
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CROSSREFS
| Cf. A065854.
Cf. A084742 (least k such that (n^k+1)/(n+1) is prime).
Sequence in context: A073081 A094928 A178984 * A182731 A101772 A158894
Adjacent sequences: A065504 A065505 A065506 * A065508 A065509 A065510
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KEYWORD
| hard,more,nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 26 2001
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EXTENSIONS
| More terms from T. D. Noe (noe(AT)sspectra.com), Jan 22 2004
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