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A065507 Smallest prime q such that (p^q+1)/(p+1) is a prime, where p = prime(n). 19
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; text; internal format)
OFFSET
1,1
COMMENTS
It is known that for the prime 97, a(25) > 31000. - T. D. Noe, Feb 13 2004
LINKS
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
MATHEMATICA
Do[p = Prime[n]; k = 1; While[ !PrimeQ[ (p^Prime[k] + 1)/(p + 1)], k++ ]; Print[ Prime[k]], {n, 1, 15} ]
CROSSREFS
Cf. A065854.
Cf. A084742 (least k such that (n^k+1)/(n+1) is prime).
Sequence in context: A073081 A094928 A178984 * A182731 A267518 A101772
KEYWORD
hard,more,nonn
AUTHOR
Vladeta Jovovic, Nov 26 2001
EXTENSIONS
More terms from T. D. Noe, Jan 22 2004
STATUS
approved

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Last modified March 19 07:21 EDT 2024. Contains 370955 sequences. (Running on oeis4.)